You may be exactly right. If I had this to do over again, I would have kicked her out as soon as I learned of the affair and that she was not willing to end it. I too thought at the time that taking a tough stand like that would just push her more away. I was wrong, it made me look weak and accomodating. However I can't go back and change the past, only learn from it.
One of the things that concerns me a bit now is that after she moves out, if she does have a change of heart and wants to come back to the marriage will that be something that I really want. I have already detached alot and also I have not really dealt with the fact that she has committed adultery three separate times in the marriage. My trust level with her is pretty much destroyed. Not sure I want to go through the next 30 years of my life constantly looking over my shoulder wondering if she is really being faithful.