I guess I'm a bit confused on this myself. If I have no control over W's behavior, how do I set a boundary that she will not respect? She decided 6-months ago that our M was over and has just been planning her exit strategy. We had a talk the other night where she brought up the subject of her moving out, and I responded that that was probably for the best. I don't think she expected me to go along so easily.
You might want to start with "I'm not going to have you texting another man in our marital home. If you can't control yourself, you can take a ride down to the corner and do that -- it's incredibly disrespectful to me and the kids."