As for contact the other woman. I didn't do it personally, but I gave my 23 year old son the phone number, and he did it. He called her early in the morning and told her he knew about the affair, and she'd better stop because he couldn't be trusted not to stop her himself! She called my H immediately and broke up with him. I still laugh every time I think of that.
My son is a pain to live with, so I figured if she wanted my position, she ought to get to know him. There are few things that he has done that have made me as proud of him.