In retrouvaille, emotions are shared in a controlled way by writing them in a set format.
Is that something that could help? Maybe he wants to say something (nice, that is), but is stuck in a pattern of meanness that he can't shake. One book I read suggested that the worst thing that you can do to a man is make him ashamed (and for a woman, to make her feel isolated). IF that applies here, maybe he is actually ashamed of what he has done, but is afraid to risk apologizing.
I guess I'm thinking aloud, so be careful reading what I write...you know your sitch the best, but why would he not want to leave if the M was over in his eyes and he wants a R with another woman?