The best advice I can give you is to go in for some radical honesty. Clear air is the best gift you can give to yourself and W, and the best chance to have an amazing new M, because that is what you are building now. Make it what you want.
(1) Tell Sally all your deep dark secrets, even the ones you think she can't stand. She will stand them, she might be hurt or angry, but she can stand them. The fallout now is far worth the clear air in the future. Don't let the secrets taint your new start, and don't fool yourself, they will. This is a magic point in time for both of you — honesty and forgiveness will build intimacy and make space for a clean shiny new future. Reclaim your best self.
(2) Ask Sally to share her deep dark secrets.
(3) Tell Sally what you were getting from OW that you weren't getting from her.
(4) Make sex radically authentic and honest. Tell her what you want. Work with her to figure out what she wants.
(5) Have a clear action plan shared between the two of you for the next time you want to self-medicate with some sort of infidelity. For instance, you need to be able to communicate this to Sally, "Sally, I'm really freaked out, I started fixating on OW today/wanting to hit on chick at bar/whatever... I know this is a symptom of something bothering me in my life and probably in our R, but I'm not sure what it is..."
(6) Read Five Love Languages.
(7) Accept that Sally has a LOT of healing and forgiving to do. As she feels safer, her anger may come out more, and it will probably last longer than you would like it to. Recognize that her anger is actually a sign of increased trust and intimacy — without those, she would hide it from you. When she is angry, what she wants is honesty and reassurance. Reassurance. Reassurance — of your love for her and her desirability.
(8) Have a lot of great sex. Push Sally's boundaries, but don't break them.
(9) Be an open book — totally transparent. Share your activities without being prompted. If you are going to be late, let her know, don't let her wonder.
(10) Watch out for old patterns that you don't like. When you start feeling the old weight of the old M when you and Sally are doing an old dance, point it out, "Ugghh, Sally, we used to do this all the time. I really don't like it. Can we try something different?"
