Dingo, I think you make some really valid points. I am no expert, as I am muddling through my own mess. If it is any help, I will say this...
The only person that really knows you and your situation is you. Even though it might seem like your W is a different person, you probably know her best...even if it might seem like "mind reading" or putting your own "spin" on what she is saying, there probably is a bit of truth to what you are thinking/interpreting. Sometimes you have to go with your gut and do what You feel is best. At this point, do you have any more to lose? I have done some DB'ing things and they have worked and I have also done things that aren't exactly DB'ing and they have also worked.
I also agree with you statement that even though your W may have OM, she probably had a reason for doing what she is doing. She probably is hurting a lot. From my own experience, I realize why my H would find comfort in someone else. I'm not saying I condone his behavior or agree with what he has done but knowing where I and we went wrong in our R, I understand.
I think there is alot of really great advice and input on everones' posts and think it's great to take all input into consideration but in the end this is your life and your journey. Do what you think is best for you. Sometimes you might get it right, sometimes you might get it wrong. You won't know unless you try.