Lyn if you want to get him to leave it is very very simple. a woman has all the advantage in the world. All you need to do is be afraid of him, or what he will do. you can change the locks on the house and file for protection and he will never be allowed back in the house until you say so.
I am not suggesting this as a course of action, but it is done every day. There is no need for actual threat of violence - all you need to do is voice a fear of it. No prior incident is required either.
This is very provocative and so I would not recommend it as a way to negotiate with a person who you think you would like to retain as a spouse.
A better way might be to talk at him, even if he refuses to talk. You could state your principles - and your requirements. "This is not a healthy marriage for me any longer. You are intimate with someone else and that is your business, your choice, but I don't accept it in my marriage."
I had a clear line on the affair thing. When I knew it was happening, It was not something I could "let slide." It was for my own self-respect.
But that kind of thing is sort of counter to the DB philosophy, which is "no ultimatims."
