This is a very tough situation for you. I'm so sorry you are having to go through this. I think what you suggested about the zero contact is the absolute best way to go. His ambivalence is torture, I know. He isn't wanting to do the no contact because he doesn't want to lose either of you. He wants to have his cake and eat it too. That's why he asked for an open marriage. But life just doesn't work that way. He is being very selfish and immature. I can't imagine the heart break you must be facing right now. I want you to know it isn't you at all. Please know that. It is him. He has some issues he needs to work on. And unless he does, then this will not stop no matter who he is with. Whether it be you or her, he will continue to have affairs. Because it is him who needs to be fixed. It isn't that you aren't any good and that she is so great. Sadly, it really does have nothing to do with you or her. It has everything to do with him. He is broken inside and only he can fix it. But first, he needs to face that he has an issue. After that, he needs to be willing to do the work. It is a difficult task and not many people are open to accepting they need to change. Unless he does, this will never end. What you asked for isn't unreasonable. So please don't back down from that request. The least he could do is respect you enough to do that. I'm not sure he will though. If he doesn't, I would suggest making the decision for him. Walk out of his life and let him sleep in the bed he made. He will eventually see that he made the wrong choice and may (will probably) try to come back. I guarantee if you allow him back in your life, though, he will not only lose respect for you, but will also continue to do this. Like I said before, he needs to fix himself. Please stay strong through this. Keep your boundaries. You can and will get through this. You are made to be resilient. Much love to you!