If things got a lot better b/c you made wonderful changes in yourself but then stopped improving and fell back into old patterns.....that's where you messed up. However, if she never stopped making contact with OM from the previous A, that's the problem.
You said he had been a friend of yours. Is he still in the "circle" of friends that you & W socialize with, or was he completely cut out of sight & sound?
I will let Puppy explain about the exposure, but I'm thinking that it is going to take a whole lot of tough love (boundary setting/enforcing) along with it. Exposure is a critical step but you've got to have these other things ready to put into place, too.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!