Still processing from last night. The quick notes are that I confronted W with my boundary statements:

1) I am not willing to live in an open marriage
2) I am not willing to live in a marriage where my partner is having an affair
3) If W was willing to completely end A, cut off contact with OM, go transparent and come with me to counselling then I was prepared to work on any and all issues that led to the breakdown of the marriage.

I told W she needed to decide what she wanted to do with her life.I told her that she could have some space and time to make a decision, but my boundaries were clear and I would not be participating in our marriage as long as she was still in an affair.

W cried and told me I was a good man, and she was so sorry for hurting me etc. She that considered her real life to be with me and S4 and that she was so scared of losing us. She said the A was a fantasy that had grown out of control. She confirmed it had started out as an EA when we were both burning the candle at both ends during our academic programs, but it has now progressed to a PA.

But she did not promise to end the A. And we left it at that for the night. I checked her phone this morning and she'd definitely been texting with OM after I was asleep, though she'd clearly erased the bulk of the messages.

Today I was friendly, got her a coffee, talked a bit about work and then left. Tonight I'm going to head out for a run and then maybe meet up with some friends for a beer later.