I know exactly how you feel op. Thought I could stay civil and spend Christmas with stbxh the few months after we split for DSs sake.
But his behaviour to me in terms of visitation, control, lack of maintenance and all the bills he left me in the shit with when he walked really coloured my view. And the thought of spending the day putting on an act and cooking a fucking turkey hot and sweaty and tearful in the kitchen while he lay on the floor building Lego as dad of the year did not sit well with me.
I changed my mind and told him no. DS and I spent the morning together. It was a bit sad and hard to do but much less stressful than having bitter feelings and a massive arsehole say on my couch, scoffing my food, invading my space and doing fuck all...
Then a dear friend invited us for lunch. And we enjoyed being spoiled in their family home.
Stick to your guns. Tell him no. Alternate years of Christmas and NYE, and if he wants to go to court, good. Then you can both get on with parallel parenting and rebuild the future relationship with your DC in your own way.
Most of the time it's hot air and blustering. You haven't done anything wrong so why worry about threats?
This year it's my turn for Christmas, and he was supposed to have DS for NYE. DS doesn't want to go, as my family arrive the day before. So I told him he could have the time between. My DS decided this. He's 12 and he knows what he wants.
He is mucho pissed off because he'll have to take work holiday to spend time with his own son. Well I do it every holiday, sick day, school training day. He has to take 10 days a year holiday to spend with him.
Was never that interested in Christmas until realising it was a way to control me (I am absolutely fanatical about it and he knows that). Had to force visitation on him. Not seen a spot of maintenance, I'm paying so far 19,000 in divorce bills and he's ignoring all the court orders and refusing to contribute. So you know what?
Tough titties. He can ram it.
When he plays by the rules so will I.
Sorry but harsh I know. But it really irks me.