I think what bothers me is that D sees his behavior. I want to be a good example to her and show that when the going gets tough, you do not stop trying.
Just another way of looking at this - why aren't you thinking "I want to be a good example to her and show that she shouldn't accept emotional abuse and infidelity from a partner?"
How would you feel if she had a boyfriend that was treating her the way your husband has treated you? Is that what you want her to learn, that this is ok?
Now - a boyfriend is not a husband, vows are vows, and I understand you wanting to stand especially since it seems at least remotely possible that he might come out of the tunnel at some point. HOWEVER, your message to your daughter should not be "Keep trying no matter what". The message should be "I had a lot of good years with your father and I think this might be temporary MLC madness, so I am trying to wait to see if he can come out the other side. But don't worry, I am not accepting his behavior, and if it doesn't change eventually, I will move forward with my life. " Or it might even be "this is what I have to do financially right now because I can't afford to move out, but I am focusing on my own life and not letting him wear on me".
