How long has he been seeing this OW? I'm thinking that you are his "excuse" to her wanting something of a commitment from him. In fact, I bet if you were to tell him you've decided to let him go and have a life with her....he'd cool his heels fast.
IMHO, if the LBS would stop pursuing the WAS, the affair would end quickly. What are some things you could do toward GAL for yourself and showing you don't need a R with a man who wants another woman?
What 180's have you been doing?
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!