God Debris
moral standards are set by God - that is, for an act to be right is for it to be an act God wills us to perform, and for something to be morally good is for it to be approved of by God.
What are these moral standards? Are we talking the ten commandments or a version of such? As you state later this isn't always clear. Following this idea, it seems we are stuck playing a game of which we don't even know the rules. A game designed for us to lose, simply because this God, has deemed it necessary to punish us for eternity for a deed we do not even understand. The original act of depravity we have committed must have been extreme, for a God to punish us so for eternity.
This God does not seem omnibenevolent at all then. If she were, then wouldn't she seek to rehabilitate us rather than to punish us? Or is this a do some evil for the greater good type scenario? In which case this God is capable of evil. Therefore, cannot be omnibenevolent. A God that freely allows us to wallow in our ignorance, and allows all the evils of the world to occur to us, on random chance (think of children that die too young, or suffer needlessly in isolation and despair in parts of our world that have the lowest of standards of living); is not a benevolent God. The fact that we are left ignorant in our depravity, deprives us of the very opportunity to correct our wrongdoing.
But, you did mention that this God loathes us anyway. We are hated. And we deserve it. This makes God vindictive, not benevolent. A benevolent God would not watch us suffer. This instead sounds like the work of a sadist.
No, that's not the main goal at all, that's simply an opportunity we have been given. An omnipotent being has no problem realizing her goals - she could eradicate our depravity in the blink of an eye if she wanted. (Plus it is not always clear what the right thing to do is, yet it would be crystal clear if rehabilitation was a primary goal). Again, we are not living here for our benefit - the idea that we are is heretical for it supposes that God was incapable of giving us such benefits absent the harms, or that God is an arsehole and only likes giving people benefits if she can harm you as well into the bargain. Either thought reveals a corrupt nature on the part of the thinker. The goal - which she could realize in any way she wanted, but has chosen this way - is to protect others from us and to give us our just deserts.
Our existence then is pointless beyond the act of just serving out our time.
And yes, I can see the logic of the form of your argument
if we accept the premise as true.
Again, that's pointless and arrogant. The meaning - the purpose - of your life is not in your gift. Any purpose you want your life here to serve is impotent to make that the purpose of your life, for it is too late on the scene.
This is a matter of perspective, and only true when accepting this premise.
Personally, I'd rather find /create meaning in the act of my rebellion, and decorate my cell. This God can piss off, she doesn't care anyway, and neither should we, hey?