I'd like to 2nd what everyone else has said...you have to take care of yourself.
It's hard to say from the outside but it seems an awful lot like your H has you on a string and he knows it. He knows that you won't give up on him and he takes that for granted. It might even make his leaning toward the OW easier. But I also understand your conflict: when you pursue affection you tip your hand and give him power; when you don't you are, in his head, cold and depriving him in some way. Damned if you do; damned if you don't.
But then that is where I also agree with what others have said. This isn't about you and it seems like nothing you do will bring him around. You shouldn't be nasty to him but is it time to do your own version of WAW? Just start putting *your* needs first and include him when/if he show signs of committment to his marriage? Personally, and I'm clearly overstepping my bounds, I think he is being a selfish, childish, wishy-washy d*ckhead. If life is *so* bad with you, and I doubt that it is, then a real man would flat out leave instead of jerking you around and taking advantage of you for all of this time. That's really close to abuse if you ask me. Anyway...
...that old nugget about "the only thing that you can control is yourself"...
You've said before that when you detach and start looking out for yourself he starts sniffing around like he is interested again. Maybe you need to start really focusing on detaching again? Even if it is not directly for DBing purposes...even if it is just to make yourself healthy. It seems like you are really struggling lately and even doing the dirty work for him (confrontation, ultimatums, etc.).
As you and the others have suggested, please get back on the DBing bandwagon and start thinking about how you can help *yourself* with some GALs and 180s. I'm sure that we all want you to be happy and, from my perspective, it looks like you are wasting your time trying to convice him of anything right now and only making yourself crazy.
You are really a tough person, even though I'm sure you prefer not to have to be, and are an inspiration to the people on the board for whom the DBing process is either slow or stalled. If we can learn anything from your patience and fortitude then we are all much better people.
Take care of yourself, WCW. I hope you have a really great time on your trip.