From reading your story here you have been way more patient than I could have been. But that's just me & my tolerance level.

I truly do hope your marriage works out, for all involved. I actually think meeting this man for a talk is a good idea. Maybe ease into the question of what would his wife think of all this. More info about these things is always better, might help both you men make a decision, some changes, ect.

You use the word bipolar, has she always had problems with mood swings or is this just how you perceive her behavior involving this man?
Reason being that bipolar is a very real diagnosed illness, usually treated with medications & therapy, just curious.

Best wishes.