Hmmm...I don't know if I have any great advice, so I thought I'd comment to see if any vets can respond.
But the other thing is you can never KNOW that he is not going to remove her from his life. He is just appearing content now. It's part of his fantasy life, even if he is working with her. At some point, there will surely be a blow-up about something, they cannot be content all the time, this is only a honeymoon phase.
Sorry 3, I know the A part of this is the really s*cky part.
Me:49 H:47 S: 16 T:27 M:25 My EA: 2001 His PA: 10/2007, 6/2013 Separated, but H still in house
Find your Shambala: a place of peace and happiness.