NM, as the husband of a bipolar woman (who in November of 2004 was convinced that she was Satan), let me strongly advise you not to ask him about any past problems. I also wouldn't ask his mom. It really doesn't matter, because an affair is really a kind of mental illness in itself.
My advice to you is the same as it's been for months: get some distance between you. I really think that SO will change, but he's going to have to face reality, which will not happen until you are gone.
You cannot "rescue" him from his sitch, NM. He's going to have to want help before you can give it to him. Read this page if you're worried about him being suicidal or something. Don't be manipulated by his weirdness.
