No one incinerates themselves, except maybe a suicide bomber. You are claiming that God carefully (with malice and considerable forethought) created a most cruel and heartless future for the majority of humankind. A crime worse against humanity that is a thousand times worse than anything humankind has ever committed against their own kind.
Even humankind has laws against cruel and unusual punishment. And correctional facilities are intended for that purpose, to correct the behavior. What is the purpose of hell? Two minutes in a place like that with the threat of possible return would be enough to correct any behavior.
But you claim it will be for all eternity with no hope of escape. And that seems peachy keen with you. After all, you figure they had it coming. (and so did you, right?)
Your second paragraph actually aligns with UR somewhat. And this is the scripture you were looking for. An afterlife determined by judgment/testing/correcting of works.
Romans 2:14-16
(Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law. 15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.) 16 This will take place on the day when God judges people’s secrets through Jesus Christ, as my gospel declares.