GEL, it's no wonder you understand the Cemar sitch so well... he really needs to listen to you and take your suggestions, because you are a witness to where his marriage will end up if he doesn't say something.
I know it's scary to put ourselves out there and say what we want. I too have been stuck in resentment (not just in this R, but in past ones, too). It's so easy to think you know how your partner is going to react and know what's going on in their minds and act the whole thing out in your head without giving them a chance.
