Oh my. I don't know how you've done it for this long. It's time for him to figure out a way to do Christmas another way. There's no way that I would be able to be around my ex.
My husband's ex-wife moved here a few years ago, and we were expected to do grandkids birthday's, etc. around her. I put my foot down and stopped going when she was there. (Which is ALL of the time.) My time is too valuable to spend it with someone that I can't stand to be around.