I have two points of view for you on this. First, as a former LBS who's H had an A. Next time he pulls the "I want to work things out if only you do...." Put it back in his court. You have taken and will take responsibility for your part in this mess but he needs to own up to having an A. You did not make the choices for him. He made them all on his own. Until he's willing to be honest about that, there isn't much to discuss. Absolutely, do not bring your kids into this anymore. Let him know that it's not healthy to drag them into your marital issues. If you need a third party, try MC again.
Second, as a child of divorce. My parents got a D when I was 19. Forget anything you've heard about older kids taking it better. It totally messed up what I thought about the entire foudation of my life. I acted out in very unhealthy ways to deal with my pain. I know now that my first marriage was a reaction to my parent's D.
You are handling this as well as anyone could. Decide what you want in a marriage and don't settle for less. Keep reading RR and the other books we've all recommended. It will help you gather strength when you have to interact with him.
