Well, this topic has consumed generations of thinkers.
If you are trying to escape from cultures of superstition, Nature is looking good.
If the nature arguments are asking for you to submit to something beyond your understanding, that is not good.
For what its worth, Socrates was struggling with the problem back in the day and he was careful not to step beyond what he could wrestle with.
I am sticking with his approach until something comes along to blow it away.

I agree when Yano says:
"From this dynamical perspective, subjectivity and objectivity rather mean which has a stronger role between subject and object: there is no pure subjectivity without object, nor pure objectivity without subject."
The previous question I put forward about how to understand epistemology was offerred because that term is commonly used to distinguish people who "know" things from what they hope to learn. So, as a matter of use, the one who knows is the subject and the object is thing that gets understood. One does not have to refute Yano's observation to permit the usage. On the other hand, there is a tension between accepted uses of object and subject that makes the term "epistemology" questionable. Not in the sense that thinkers should decide to abandon it or not, but in the sense it needs to carry its own weight, explain stuff and not just assure thinkers it is self-evident, etcetera.

I don't have the chops to defend or dismiss the arc of philosophical systems since the appearance of Kant. But your comment does remind me of two teachers I had in college. One was very dedicated to Kant and he said the following about Hegel:

"The man invites us all to play musical chairs, gets the band to start the music, and then refuses to let anybody ever sit down."

The other teacher was a scholar devoted to Plotinus who wondered:

"it is possible that the entirety of German philosophy since the Reformation is merely a byproduct of growing up Lutheran?"

I was blessed to be surrounded by trouble makers in my youth.

Strictly speaking, Hegel is not agreeing with your first point: "A thing-in-itself would have to lack all determination." (emphasis mine). The "would have" implies a conclusion where as Hegel is not finding the result out but reminding the thinker how it got to the thought in the first place.
In that sense, he is agreeing with Wittgenstein.

The chapter on The Critical Philosophy in Hegel's Logic shows Hegel going in the opposite direction from an isolation from experience as suggested in the statement: "engaged in making sense of the world by imposing our a priori structure on it." It needs to be read in the context of the whole chapter to be properly understood but Section 52 gives a sense of the direction Hegel is headed:

"in this way thought, at its highest pitch, has to go outside for any determinateness; and although it is continually termed Reason, is out-and-out abstract reasoning. And the result of all is that Reason supplies nothing beyond the formal unity required to simplify and systematize experiences; it is a canon, not an organon, of truth, and can furnish only a criticism of knowledge, not a doctrine of the infinite. In its final analysis this criticism is summed up in the assertion that in strictness thought is only the indeterminate unity and the action of this indeterminate unity.

Kant undoubtedly held reason to be the faculty of the unconditioned; but if reason be reduced to abstract unity only, it by implication renounces its unconditionality and is in reality no better than empty understanding. For reason is unconditioned only in so far as its character and quality are not due to an extraneous and foreign content, only in so far as it is self-characterizing, and thus, in point of context, is its own master. Kant, however, expressly explains that the action of reason consists solely in applying the categories to systematize the matter given by perception, i.e. to place it in an outside order, under the guidance of the principle of non-contradiction."
Translated by William Wallace

Hundreds (thousands, millions, if you are counting) of years of slavery. How much was enough? Toward what purpose?
Stupid stuff we tell our kids. I try to not do that and I often fail. What is that about?
We live in a place we are sort of prepared for but little of that preparation gives a crap about what is happening to us or people we know.
Our life here is not just about whatever concerns us when we are challenged as individuals. It is also this mess that we have inherited. And we give to our successors.
I humbly propose that some things require further investigation.

I agree with your last sentence. I have trouble with the first one.

There are a number of ways to approach this. I propose two of them as possible reasons to frame the topic in other ways than you have rather than as a rebuttal to what you have proposed.

All the reasons we hurt each other are not necessary to understand that suffering is part of being better or learning stuff. Unnecessary suffering is cruelty that serves cruel people. It is what has been going on for a long time. I accept that making universal claims on no other basis are problematic but I don't recognize a world where this element does not shape what I see.

Many people (probably myself in ways I don't understand) repeat the beat downs given by others. I see this clearly as something that is happening. Things get darker when I try to explain it. I don't have to explain everything. I am involved when I look away from something.

As a matter of full disclosure, I practice a kind of faith. An important part of the "Lord's prayer" is where it prays one does not get tested too much.

Anyway, there you have it.

It looks like there is some disagreement about what is "inherent."
Maybe I am slow and I am certainly new here but I am not getting a self-evident experience here.
Help an old guy cross the street.

Isn't Jake asking you a question?
If you are putting on shoes, it is time for the other foot.

But, is suffering inherently meaningful? I think so.

Metaphorically it's a ladder everyone has to climb on. — Posty McPostface

I am trying to say it's value depends on situations and points of view. There is a way I can understand it as a ladder. But I have seen it as a kind of prison too.

I have been lost between too many camps of epistemology to be sure what "inherently meaningful" means for me or others. So I think about it in terms of exchange. Is suffering a valid component in any kind of exchange?

When I put it that way, I can strike a lot things off the list without hesitation:
I cannot build up a reserve of the stuff to pay for better lodgings in another plane of existence.
It is not valid currency that can be given in lieu of something else that is needed or desired by others, like affection or patience. Now, being patient can cause suffering but that is not what is given.
People do suffer things so that somebody else won't but that needs to separated from Item #1. Martyrdom requires a certain currency.

Suffering is a part of learning any art or trade. I have seen "geniuses" who somehow learned with greater ease than others but they too had their own baggage. In terms of currency, this does not have a one to one correspondence to receiving any particular benefit. I am an accomplished builder with many years of experience, it amazes me how stupid I can still be. There is a terrible expression some of us in the trade use when suffering does not confer much knowledge to a colleague: Rookie for Life.

I take your point regarding proximity not being a valid determinant of what is objective or subjective. In raising it as "one context" (that you asked for), I hoped to point out how the distinction is used in many instances.
In regards to your opening remarks, I am not trying to reference other discussions (which are interesting) but trying to understand what epistemology is supposed to mean in your version of the word.

It is difficult for me to see the original question without starting with the question of whether the psyche has a nature that can be studied at all. The "subconscious" is part of a model. Is it stupid to work on these kinds of models?
In the pursuit of that question, it may not be useless to point out models made to explain behavior in the most general sense of the word are not the same as those developed to try and help people in real time with awful problems. Freud and Jung had patients. Skinner created some.

One context where making the distinction happens is between events that are disclosed to all who are close enough to perceive it and events that can be hidden from others because it happens to a particular individual. Of course, when I put it that way, all events are equally real in so far as they are experienced.
So the argument against private language in Wittgenstein, for instance, is not a denial of the reality of private experiences. It just puts talking about them in a particular light. Also, many of our language games play on the theme that what seems private may be easily perceptible by others.
Many choose silence as the way to be alone.

I see the matter as what Kierkegaard refers to as "earnestness" He wrote:

"Therefore nothing can be said about earnestness in general. It is not pure subjectivity or any similar stupidity. Earnestness is present only in the very finest concretions (the empirical self) and as a qualification of freedom. To speak of freedom in any other sense is a misunderstanding. There is no measuring rod more accurate for the determination of the essential worth of an individuality than that of learning what in a pregnant sense made him earnest in life, for with a certain kind of earnestness one can deal with various things, except that from which an individual dates his life. Earnestness about the national debt, about one's own debt, or about astronomy, etc. A healthy spirit manifests itself precisely in being able to deal with everything just as sentimentally as jocularly, and just as well. But in relation to earnestness, it tolerates no sentimentality and no joking. If it does that, it will happen to such a person as with Albertus Magnus, who boasted of his speculation and suddenly became stupid."

From Paper V B 65. as a note in Concept of Anxiety translated by Reidar Thomte and Albert Anderson.

Or maybe it is a viable idea but needs further qualification.

Some people sincerely believe bad things. Not just in the sense that they are wrong (a discussion in itself) but that those beliefs make them whole, in their mind.
People make choices. The possibility that gives you happiness is handing out other outcomes at the same time.
The importance of the theme of self knowledge is that it is the only thing pushing us toward taking responsibility for what happens.
And thus all the arguments about what is true for oneself is immediately entangled with other people's truth.

That's right. Nietzsche saw values as getting closer or further from supporting the life of the one doing the "valuation."

People don't always know their own motives. I agree with gloaming (assuming I understand the comment correctly) that it doesn't happen only under a single set of conditions.
Speaking in bad faith certainly leads to poor discussions. But not all "good faith" discussions are worthwhile. What I ask myself a lot is if I am really having the problem being discussed. In that register, sincerity is a desire to go somewhere, closer or further, to or from something that a thinker thinks is important for themselves and who they love.

The wager is presented with arguments that there is "nothing to lose." As bets go, that doesn't make much sense. But Pascal does address what will be at risk elsewhere:

"Only Christianity makes men both happy and lovable: the code of the gentleman does not allow you to be both happy and lovable." (Lafuma 542)

And for Pascal, the irrationality in regards to utility is a feature, not a defect. It is repeated in many ways but here is one:

"The only knowledge which is contrary alike to common sense and human nature is the only to have existed among men." (Lafuma 604)

So the articles of faith lead to a form of life that makes its own kind of sense if one starts living it.

Pardon me, that was obscure.
I meant to say that Socrates of the Republic agrees with Gilson. While different theories are advanced and universals proposed in the dialogue, they can be understood as means to defend against the attack made by Thrasymachus who claimed that the just is to do what is for the advantage of the stronger. The work needed to seek the order that can answer that challenge is never complete.

The Socratic argument would be wondering when the sparse defense against certain propositions suddenly became an attempt to rule over others.
Maybe that did happen. But arguing for that idea doesn't illuminate the original defense.

It is interesting to compare this discussion of free will with Spinoza's proof of God who incidentally avoids the problem of free will in the conception of omniscience by denying free will actually exists.
The argument is the inverse of Anselm's from the point of view of what is possible to imagine. Anselm presents the idea of God as being so hard to conceive that only his existence makes it possible for us to do it. Spinoza presents God as being the easiest thing to imagine but that quality tells us little about either his nature or that of his creation.

I see the matter as many lines in parallel. I know people whose depression is a burden they would have gladly shed already if it wasn't for their sense of duty to others. There are some who have killed themselves to form a sentence upon others. Or maybe just form a sentence.
Some are fascinated by their fear of death and obsess over it to the point that they attract it to themselves. A number of drug addicts I knew in my youth went through this and either passed through it or did not.
Then there are philosophies or perhaps I should call them moral codes that prepare one for death. Bushido calls for one to embrace one's death so completely that it stops a process inside of you. It stops fear of death, of course, but also hesitancy to act when required. They are not far off from the Gurdjieff teaching but without all the celebration about how smart they are.
Taoism teaches you only have so much in the tank. You should worry about getting re-fills wherever possible if you are having fun and less about what cannot be controlled. They do have a section that obsesses over immortality but it is mostly there to encourage the original observation.

Having read through the whole thread, what you are calling "nihilistic relativism" sounds much like 2/3rds of Kant's Canon of Pure Reason:

"All the interests of my reason, speculative as well as practical, combine in the following questions

• What can I know?
  
  • What should I do?
    
    • What may I hope?

The first question is merely speculative. We have as I flatter myself, exhausted all the possible answers to it, and at last have found the answer which reason must perforce content itself, and with which , so long as it takes no account of the practical, it has also has good cause to be satisfied. But from the two great ends to which the whole endeavor of of pure reason was really directed, we have remained just as far removed as if through love of ease we had declined this labor of enquiry at the very outset. So far, then as knowledge is concerned, this much, at least, is certain and definitively established, that in respect of these two latter problems, knowledge is unattainable by us.
The second question is purely practical. As such it can indeed come with the scope of pure reason, but even so is not transcendental but moral, and cannot , therefore, in and by itself, form a proper subject for treatment in this Critique.Critique of Pure Reason, A805, Translated by Norman Kemp Smith"

In making these distinctions between "uses of reasons", Kant wasn't interested in Descartes' musing over whether the people moving outside were actually automatons but in finding a way to protect using logic from Hume who argued causality was an arbitrary association between events. Kant also was keen to have the products of mathematics accepted as valid without having to prove more than what they claimed for themselves. It is with this matter of uses in mind that I consider your reasoning:

"P1: The application of logic requires premises
P2: Any conclusion the application of logic leads to is true if the premises are true
P3: There is no way for a premise to be determined true or false except relative to another premise
P4: A premise cannot determine it's own truth value or if it can then none have been found so far that do so and are useful in proving anything else
P5: There is more than one potential premise from which someone can start an argument.
P6: Consequently there is more than one potential premise that can be used to determine the truth value of a premise
C: More than one conclusion is valid if the right premises are used to determine it's truth value."

The problem with P3 is that it voids the reason for making any proposition. In a math proof, for instance, how the premises are developed to demonstrate a separate claim than the premises is why the syllogism is more than a list of assumptions. I am repeating Metaphysical Undercover's observation that your reasoning is circular but adding the point that nobody uses reasoning the way you describe it.