Hi,
I found that getting into a routine, even though it wasn’t the one I’d planned, helped a lot. After a few months my ex became less threatening too. I think once he realised I wouldn’t stop him seeing his son, and when I didn’t react to his more unreasonable demands, he couldn’t be bothered any more.
And once I knew how much effort Ex would make on his own, I could set my son’s expectations, and be ready to make up any shortfall. It’s a balancing act but it does get easier.
on the Xmas thing, I have to admit, I take a bit of a liberty though. My ex refuses to do sports days, school plays, parents evenings, doctors, dentists, shoe shopping etc. although we both work full time. So in return I claim Christmas Day every year. He gets the five days between Xmas & new year. (Son is 10).
But find what works for you. x