If god cannot be tested then no one can claim to know that god exists. Suppose that at the time you were praying for your dog I was also praying to a doorknob. How would we know which answered the prayer? How would you determine whether anything answered your prayer? If you have accounted for all possible outcomes then your belief is unfalsifiable and therefore has no standing in a community that does not already share your commitments. However my biggest problem with this is ethical and religious. To turn god into something that looks out for you is to build an idol out of need. To praise god for delivering what you want is to make god blameworthy for all the shit in the world. You cannot praise that which you cannot blame. I do not write this as a believer or unbeliever because i actually think it is idolatrous to treat religion as a belief system. What I can say is that I lack a need for such a deity and that this lack of need may be exactly what allows one to be truly religious. And by the way, the other problem is that there is no god swatch with which you could compare a supposed deity to know if it is the supposed deity.

The question is not “are we allowed to dispute facts!” as if that word stands for everything everywhere that are facts. The question is “how do we determine what counts as facts?” And that will always be contextual. We also cannot choose to believe some facts because we “assume” some things at a preconceptual or prefactual level. These are sometimes called basic beliefs or hinge propositions though they are neither because they are preconceptual. They are the things that make it possible to believe or doubt because they determine what belief or doubt amounts to. One can not ask “should we believe these things because they are facts” but rather based on “facts” we live out in life what other things ought we to believe. The OP presents this question as though facts present themselves to us as a monolithic thing. Is it a fact that 7 is a prime number that we ought to believe? Well, if we are engaged in mathematics then we have to so regard it or we will not be doing something that we call mathematics. On the other hand, if it appears on a bingo card it is not only not a prime number, but not even a number because you are not using it mathematically. An image of an animal would work just as well. To ask if we ought to believe facts is similar to asking ought we to use our legs for running? We do “believe” and that is what makes facts and fictions possible. Can one always ask “is that a fact?” Sure, but not in a meaningful way. Take the question, “are you trying?” That can be asked infinitely of any endeavor but that does not mean that you were trying any particular endeavor. It is an illusion of a meaningful question because one can put the words together.

People should stop taking The Great Arcanum seriously. I’ve never heard such gobbledygook in all my life. I will say that his approach is very effective at driving people away from theism and that is not a bad thing. There is no place in philosophy for calling people “fools” and “propagandists”. When he said that about Wittgenstein I knew he was a nut.

I think it was Hume who successfully devastated any and all teleological arguments for God. In addition I would suggest that the OP's version relies on the infinite regress that is always possible with certain problematic concepts. In this case, that concept is the concept of "try." It makes sense to say that I tried to do x but it makes no sense to say that I tried to try (or I tried to try to try to try). That it makes no sense is not immediately obvious since the sentence seems sensible. The same is true of other concepts like "believe" and "interpret." I would also point out that the only important thing about pointing out that existence is understood before non-existence is that it reflects the truth that belief precedes doubt. The OP seems to subscribe to an essentialist or Platonic view of concepts that simply does not hold up after Wittgenstein. I would not get into the weeds with this argument any more than I would about an argument over which reindeer flies the fastest. Lastly I would make the old argument that the attempt to make belief in God reasonable is a form of idolatry that distorts the God one is arguing for in a way that makes that God monstrous at worst and uninteresting at best. Job's friends come to mind.

I agree with just about everything Sam26 has said. I would not use the term "foundations" to characterize Wittgenstein's bedrock propositions but then I don't want to call them "propositions" either. I am not sure that they are pre-linguistic because I think that even bedrock "propositions" can change or evolve over time and it they were truly pre-linguistic, I don't think that would be the case but I am ready to be persuaded otherwise. Wittgenstein gives an example that goes something like "no human has ever visited the moon" which of course is no longer bedrock but would have been through most of human history. I also wonder about notions like up/down which are probably bedrock for any human living on earth but might not be if future humans live in space. I am totally spitballing here as I am new to this forum and do not have my copies of OC or PI with me. I do think that the issues Sam26 addresses are some of the hardest to understand and are consequently, the most misunderstood in Wittgenstein's philosophy.