There is one ingredient in this exclusive dating you may be missing. To a WAW, the most desired and pressing issue for her is......FREEDOM. She can't see freedom in exclusively dating her H.
Exclusive dating, for her, would be no different than being in the marriage. Therefore, it does not appeal to her. It may not be "you" as much as the idea of losing her freedom and independence, as she sees it.
I am not suggesting that you should be one of her BF's. On the contrary, I think you should drop that blasted rope and move on with your life. You feel as if your life and your M has been on hold, right? She may have cheated, but you are the one who put everything on hold.
I have a new 180 for you. Stop trying to get her back.
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!