What I find interesting is, if this guy came onto the board saying things like "I don't know why I treat her like this...." and on and on from HIS point of view, we would all probably be giving him advice on how to save this relationship in light of the fact that he may be bi-polar, or something.

But that would be wrong. Littledolly, he is likely going to try and sway you to start seeing it that way. You don't need it. From your description, he has crossed the point of you benevolently helping him "get better". It would all be at your expense and his pleasure if you stay. Get away.