The best would be, when he asks back into your home and into your life, for you to say "I'm afraid it's not that simple anymore." Then let him twist for a week or so, and then let him come back WITH CONDITIONS:

- sends no-contact letter to OW
- complete transparency with you -- cellphone, computer passwords, etc.
- agrees to go to MC with you

That sort of thing. If he refuses, then you tell him he's not welcome back in the home.

Had you done that, you wouldn't be in this boat. The good news is, you still have the opportunity to lay out your boundaries.

Puppy