Wow, wonderful news. Sounds like you are handling everything very well. Here's three words of advice.
1) Share with your W. You have been saying all along that you are the one who is willing to talk, but W is not. In fact, you have not been sharing with W and she shared with you. So, you are wrong on this point. I suspect in your heart you feel more willing to share, but you have been afraid to take the emotional risk. You need to be willing to open up. What are your dreams for the future? How hurt and angry were you by the A? You need to share your feelings. They will keep coming out. And, your hurt and anger need to acknowledged, validated, and accepted for you to get beyond them. They will keep coming up in different ways, you both need to be prepared for that.
2) I would very strongly recommend setting a very firm boundary with respect to OM right now. It is inappropriate for HER to be the one trying to comfort and care for OM. She is continuing to keep a third party in your marriage. I'd say it is time to make clear that it is no longer acceptable for that to continue.
3) Look, to be very straight, she almost certainly had a PA, IMHO. Your suspicion is one very big clue, people are exceedingly rarely wrong. Also, what she said last night and her behavior with you physically suggest a PA. You need to express your fears about this and be very clear in what you need in terms of honesty from her (simple yes/no, details, etc...). And, she may think she has not participated in unsafe sex when she has (oral is not safe sex.)
