Originally Posted by newtoday
You should find a forum for Managing Open Relationships/Swinging. This forum is not the place for you.
I hate to say it, but I have to agree. You're not looking for ways to accept or deal with poly. Poly isn't what you wanted in the first place, you wanted Open, so I understand this isn't what you signed up for. But it's happened, so now what are you going to do about it? You can only control YOUR actions, not his. I wouldn't issue the ultimatum unless you're absolutely ready to have him pick her and would truly prefer that result to staying and trying to find a solution that works for all parties.
Basically, your choice is: do you stay and do a LOT of work, both on yourself and your marriage? Or do you leave? Because you can't "make" him do anything, and even if he agrees to stop seeing her you'll be left with a broken relationship and a LOT of anger and resentment, probably on both sides but at the very least from him, to you.