You'd think that a good atheist should get into heaven before an un-repented sinner.
Gautama Buddha said that if you live a life of decency and good order then if there's a heaven you'll have no worries and if there isn't, you'll die knowing you've added some good to the world. I'm not a Buddhist, but if there's a god, or gods, and [he] or they are just, then that seems fair. I've never understood why Jesus' death absolved the world from sin
conditionally on belief ─ sounds like a cheap sales trick when you think about it.
Jesus said that one could get eternal life (not necessarily in heaven) for merely believing in him. But clearly un-repented sinners must not be allowed into heaven or heaven would be like hell, filled with vicious people and sinners.
Much crime is due to mental disorders and much is due to social resentments and the lack of a level playing field. Surely a god could cure the first and persuade the second to a better outlook rather than send any soul they might have to punishment and perdition?
Atheists know that believing without proof would lead to believing everything (Santa, tooth fairy, and even cartoons, like Fred Flintstone). Therefore, they believe in nothing until they absolutely have to believe.
I know what you mean, but there are many exceptions. Some people are atheists because they feel wronged by the church, not only for sexual abuse or workhouse welfare but also for discrimination against them ─ Stephen Fry, who is gay, said as much in a talk which was and may be still be on YouTube, a very angry outburst rather than a carefully reasoned theological or materialist position.
Yet, atheists seem to put more faith in science, and some scientists seem to toss ideas without proving them.
In science, you have the distinction between what is satisfactorily demonstrated to be correct, and what is hypothetical but a reasonable conjecture and therefore should be further tested. In science, both 'dark matter' and 'dark energy' are names of problems, not of solutions or identified things / phenomena, and the claims you speak of are hypotheses, promising but still undergoing testing.
But as in life, so in science ─ there are many reliable statements but no absolute ones. Science proceeds by empiricism and induction, and is never protected from unknown unknowns. Or as Brian Cox said, A law of physics is a statement about physics that hasn't been falsified yet.
So the justification of science is not that it grasps absolute truth about reality (ie the world external to the self) but that what it indeed grasps, has worked and continues to work pretty dang well.
As for religion, it seems to me that all gods and all supernatural things exist only as concepts / things imagined in individual brains. Part of a great deal of evidence for this is the absence of any definition of 'God' (or 'god') appropriate to a real god, one with objective existence. To give my usual example, there are objective tests that can determine whether this keyboard I'm typing on is a bat, or light in the violet band, or the smell of diesel fumes, or even a unicorn (and it's none of those) but no test to tell me whether it's God or not. If God were real, had objective existence, how could that be the case?