You are in a tough spot man... tough spot. Normally I would advise someone to go along if their spouse asked them to do something. However, you have laid your boundaries and kinda have to stick with them. I don't know it that applies to going to relatives for holidays or not. That is something I think you have to rationalize for yourself. Sorry I can't give better advice there.
However, one thing to think about... Your wife feels safe in this other relationship, that is most likely why she is hanging onto it. How is she going to see and feel improvements with you if there is not interaction with you. It is a catch 22. I do not disagree one bit with you establishing your boundaries. I think this was a good thing for you to do for yourself. However, again it makes it tough to move forward in a way too.
