Well, I think that's where my challenge is going to be- BOUNDARIES.
As far as the A, she has the choose the A or work on the marriage. I can't bring up all the stats or anything. She won't listen. I guess all I can tell her is she'll OWN the divorce. I 'should' own up to my 50 of the marriage problems.
I can't legally enforce keeping D away from OM.
I can't legally kick her out of house.
All I can do, if she doesn't say "M", is tell her:
"Then all I have to say is this. I will not live in an open marriage. I will not hide your lies or affair. They are disrespectful. I will send you info on a few mediators I have looked into. XXX is the best choice. I will set an appointment for as early in August as possible to draw up our Separation Agreement. I should have all my banking and documentation gathered by then. You should, too. Divorce is my last option. It is clear that it is your first and easiest. What you are doing to this family is irresponsible. But if this is your decision, then you will own it. Perhaps one day we can be friends.