I have a problem with the 3rd assumption. It presupposes a deity that is narcissistic, selfish, and absolutely unworthy of our worship.
That presupposes that narcissism, selfishness, and your general moral feelings are universally applicable. Don't you think this is awfully arrogant for a mere mortal? It seems clear that your concept of what a deity *must* be is entirely dependent on what you *want* a deity to be.
A deity is already fundamentally different from humans on many levels, so there is no particular reason to conclude that they must share our same sense of morality. Gods may delight in throwing their children into dungeons, or enjoy pain suffered in their name. Betrayal may be par for the course, who can say?
A creator that poofed everything into existence by magic and then throw the created that are "rebellious" into the pit of eternal damnation is a narcissistic creator and thus does not deserve to be worshiped or loved.
Ok? So if that was so, you wouldn't worship or love that creator. But that does not seem to be what you are saying; you seem to be implying that because you don't approve of such a deity, it cannot be so. Is reality subject to your approval?
So, according to the religious doctrine, why did god create a big ass mother fucking universe?
Why make a universe more than ~6000 light years beyond the Earth, given that we cannot exceed the speed of light and thus could not possibly reach any of those locations even starting immediately upon creation? Good point; it seems the only reason would be to rub in our insignificance.
You only have to see a mourners grieving over the death of a loved one, and you can see that it brings more pain than joy.
Well that makes no sense. I can see that mourning a lost loved one is sad and all, but is it less pleasant than being neck-deep in Velociraptors? Perhaps if nobody ever died those loved ones would be in pitched battle over enough food to satisfy their hunger.
Concluding that removing death from the equation would result in an overall better world is unreasonable without other extensive changes to reality.