I would say that atheism has already crept into the minds of some past POTUS, even if their religiosity was only diminished to deism. If you define an atheist as "any person who is not a theist", then you could say that a deist is an atheist, just like a man is an ape.
I don't know what it is like to be born gay. At what point of childhood does the realization that you are gay manifest itself in your mind? I'm sure it varies from child to child. I haven't heard of any suspected gay POTUS. Would they have been able to keep it in the closet and out of the history books if they were gay? It would be difficult, but I would have to leave open the possibility. Let's just say it wouldn't be science-fiction.
I vote "Atheist".