Note: I'm an atheist who, like you, agrees that there's no divine plan and that, good or bad, shit happens.
That said, I think there's a hole in your argument. You're convincing when you claim that unfair things happen on Earth; you're not convincing when you claim there's no afterlife where Earthly-unfairness is addressed.
Isn't that the whole idea (and solace) of the afterlife? (Occam's Razor stops me from believing in an afterlife, but you don't delve into that in your essay.) A theist could easily agree with most of your essay but say, "Don't worry... (read more)