We do not have conclusive evidence of what happens after death. My opinion is that there's nothing, but we can't be sure. It's odd sending people somewhere we have no idea of what it is, might as well be world's nicest flower garden with 7 quintillion virgins. Life sentence is worse anyways.
Depends on the prison system.
It's definitely not worse in the UK, where prison is a nicer place to be than where many criminals live.
I would support the death penalty, not for deterring people, but as retribution. I'm not saying it should be dished out willy-nilly, but there are plenty of horrific murderers, rapists and paedophiles who are nothing more than a blight on society.
I would rather have them killed than sit about in the prison system, living an easy life, while their victims suffer a hard life due to the actions commited against them. And much better than the chance of them getting out.