I have confidence that you are the best judge of how to deal with your own wife. However, I do not like for there to be misconceptions of what Retrouvaille is. It is not counseling, and should not be thought of as counseling. It is leadership by example.
Couples who have been through the misery stage of marriage and who have healed themselves lead by telling their stories. Their open, honest, heart-felt confessions of what they did and how they felt during their awful times speak to you in a way that nothing else can. Then they ask each person to write in a journal the answers to questions about themselves and their lives. It is 2 days of introspection and meditation. After answering each question in the journal, you exchange journals with your spouse and discuss what you have written. This process leads to greater understanding between the spouses. And from this better communication grows. Both spouses are reminded of some simple rules of writing to keep everything fair. You write only about yourself, not the other person, and a few other rules that keep the journals from being antagonistic.
There is no speaking in public about your problems and there is no third party listening in on your talks. You are alone with your spouse talking about your lives.
I can tell you from my experience at Retrouvaille. If you are looking for God, he is there, helping those who are helping themselves.
You make a good point. Perhaps your wife will be more open to this later on, when she has tried and failed to trap another man into being her breadwinner. Right now OM might just be enjoying the ego boost of being wanted by a 2nd woman. When he finds out that she is trying to unseat his wife and insert herself in her place, he may have to let your wife down gently. And at that time she may realize that even a broken husband is better than no husband. Especially if he is making strides to not be broken anymore.
So store the idea away. Maybe this is something that could be helpful to you later. I went to a Retrouvaille gathering of volunteers last night, and was touched by the loving interaction between the partners. These were all couples who were on the verge of divorce and then healed their marriages, and now they are volunteering to pass the gift of healing along by helping with the local Retrouvaille program. My husband and I were proud to be in that room.