THIS NOW!!!!! I agree. Get a lawyer. File for D. Get a solid custody agreement in place. Then back off and get on with your life. She wont even begin to work on herself until she feels that you are no longer available and an option in her life.
Cut off the phone, internet, all forms of communication that you pay for that enable her affair.
You need to say: "Wife, I will not live in an open marriage, I respect myself too much for that, either cease all contact with OM and commit to our relationship with counseling or move out."
THEN FOLLOW THROUGH. You threaten, but don't act. You allow your wife to cake eat, and monumentally disrespect you and your marriage. Action = respect. You need to stand up for yourself. You are being played!!!