I'm so sorry you are feeling this pain. But, and I speak as something who has been going through something fairly similar... Maybell is right. You WILL get through this and be ok.
My H and I haven't had a R talk in months, but the last time we did, he said, "I just don't see a married future for us." and "I realize now that I had been unhappy for even longer than I originally thought." Ok, then.
And yet, we get along quite well, he shares cute stories with me about our D, has been amenable to my requests for schedule changes, he even bought me an expensive gift recently (as a sort of apology). And still cannot bring himself to entertain the idea of R.
I went through what you are feeling. It's so surreal. How can they be SOOOO pessimistic and stubborn and unwilling to even TRY?
But they are. They just are. They have their OWN sh!t to work through.
When my H left me, sure, I can readily admit things were really bad. But NOW-- a year later? After I've learned so much and grown so much and given him SO MUCH space and remained pleasant and strong? He is a damn fool to remain so stubborn. Am I mad about that? Of course. Do I wish I could wave a magic wand and make him WANT to work on our R? Of course!
But I can only control me.
And so, I choose to hold my head up high. This is about HIM, much more than it's about ME. I will show my D my strength, my resilience, my ability to have compassion even for those who hurt me (and her), and model through my own changes that PEOPLE CAN CHANGE if they want to and work at it.
Yes, I would recommend pulling back from the family time, if you think that will help YOU detach. I'm now at a place where I don't think that much about him, or what he's thinking or doing (or with whom), especially when I don't see him. My triggers NOW are my D leaving to spend the night at his house, and thinking about/talking to his family or "our" friends. But he is mostly a colleague in the "D3-raising business" that we share. He's more like a colleague who I am cordial to, and at times have to work closely with and problem-solve with, but who doesn't know much about my personal life and vice versa. We are not "friends".
It's weird, and sometimes awkward and painful. But it's definitely do-able.
And has been the thing that has helped me move forward the most.
I am here for you (unfortunately for both of us!!) and so are many others who can empathize and relate. You are a great person and a great mom. You are NOT evil. You CAN work on whatever aspects of your being that you think will make you a better, stronger person. He's gonna do his own thing, in his own time.