First time on this thread...good to know you're here.. Divorce finally came through in August though we've been living apart for two years, 1 DS. Don't feel sick at seeing a text from him, never mind the sight of him, now but it took a long time.
2012 you've probably heard of it but the website outofthefog has some useful resources, I use their "medium chill" technique a lot and it works (basically you become uninteresting, not engaging emotionally, only answering in a factual grey manner). I also use their JADE recommendation ie to never justify, argue, defend or explain your feelings, views etc. This has maybe been said a gazillion times before, sorry if so.
As for the shifting goalposts on custody agreement, that's my ex's favourite trick. I've learned not to give him the pleasure of seeing me annoyed. So I defer my reply (I'll get back to you on that), don't answer texts or calls immediately unless I want to (hardly ever) and refuse to change my dates. I quietly say I'll take DS if you can't do it on your days but can't swap (with no explanation, none of his business).
After getting over the anger at him not pulling his weight (he asked for shared custody but that was only to show narc mum what a good guy/victim he is) I found the benefit of "helping" him like this is that he can't hook me into an argument as he thinks he's won and also DS spends more time with me it's better for both of us.
Have past breaking things as it now feels like any emotion spent on him is wasted energy not that I wouldn't like to run off to the other side of the world/hire a hint as some days!!
to you all