"Cheliax is the only place I've ever heard of where I can exist as myself, Hell is the only afterlife I can imagine myself going to, Asmodeus is the only god who fits me in any way. I was similarly honest when I described to you the kind of sex I like, that keeps me in my place. I've always enjoyed being forced into sex, I was never actually in denial about it, that was a lie to see if we could get you to force me into bed without my saying yes to anything."
"I went to Elysium because of my curse. They showed me what Hell was actually like for the people in it, and spent a lot of time apparently trying to talk me out of things and telling me how much Asmodeus didn't deserve me. I came back to Golarion willingly, to serve Asmodeus in this world, and then in Hell."
Because tropes sent him an incredibly improbable person or because a lot of people are actually like that??
It - probably doesn't change anything, unless almost everyone, is like that, but - if at some point it sounds at all reasonable, that any of this could come down to numbers, he's going to need that number.
And swear a cleric of Iomedae to secrecy and ask them about the probability of Iomedae ending Hell. Though Keltham would've needed to decide to destroy the world before then based on his guess, and only be considering undoing that decision, in order for him to be not using that information against the person who provided it.