Setting Boundaries for MLC Alien H

[In Limbo]

I have been posting on newcomers forum, but Sandi2 suggested I move over here. I've not yet figured out how to include a link to my original post (sorry, I'm blogging challenged), so I'll include a very brief history.

Discovered H's EA by reading emails. OW is younger, worked for H, married. At time of bomb, he was pursuing and she was saying just friends but not stopping his pursuit or professions of love. Since bomb (EA, ILYBNILWY, don't know if I want to work on M, etc.), he has moved out during the week and things have gone up and down, seemingly aligned with his R with OW (as she has accepted his advances, things deteriorate for us. We are going to MC about every other week, but he says he's just "not feeling it" for me. He has not admitted any contact with OW, but I have proof it has continued. He has distanced not only from me but also the kids, which is killing me.

I have been trying to DB and GAL, but face the same problems with detaching (so hard!) and backsliding I have read from many. I am committed to my M, but frustrated as don't feel there's a chance as long as he has hope with OW. I'm feeling played and don't want to be a doormat and thinking I need to set boundaries.

My question that I hope some of you guys that have experience and are doing so well will help me with is this - when you have MLC with EA (99% sure not PA yet), what type of boundaries can you set without pushing them away? Is it ok to discuss R and OW when it comes to setting boundaries? Anyone willing to share examples of boundaries you set that worked well to protect you and maintain some self-respect?

I'd really appreciate any feedback. Thanks!