manga, believe whatever you want as is doesn't seem you actually wish to entertain explanations for the phenomena you are discussing. You seem to be more driven by confirmation bias. If you want to believe in life after death, heaven, hell, and so forth, fine but don't keep coming here and wasting people's time with the above discussion pattern. It's ridiculous and frustrating.
manga's explanation of his behavior has been that he doesn't
want to believe in Hell, but he's so terrified of the thought of it that he can't stop worrying about it maybe being real.
In addition to therapy, which I think is an excellent and practical idea, some of us have suggested just going along with Xtianity and taking whatever steps they recommend to avoid Hell. He'll still be obsessed but with any luck he'll be less frightened, which is always good. I would suggest Catholicism -- they're the original Xtians, after all, and generally seem more accepting of worshipers having doubts.
But I don't think manga will make any more use of that than of any of our other suggestions.