I was sort of where you are except husband did file for D and had a 6 month affair (totally denied of course) that took some time to die out. He came back to the marriage slowly as it was dying out and only fully came back when it was over.
What I did was just work on being a great friend, extraordinary listener and very supportive. I also emotionally detached and "lived my own life." Although, my H was out of the house and that does make detaching a little easier. I could also be generous with my friendship because I felt I had nothing to lose and I wanted my H to someday regret his decision.
My vote in this whole thing is to work on yourself, give him lots of "leash" and just be a friend. Have no expectations. In fact, until my husband was fully committed I treated the relationship as if he wasn't going to stay. I honestly didn't want to go through the pain again so I kept distant. But I made sure I looked great, always wore a smile, was friendly to him, and just focused mostly on myself and my kids. I'd do nice things for H, but I did them without any expectations.
There is no arriving, ever. It is all a continual becoming.
