Honestly i would prefer not to communicate at all, set the dates at the end of the month for next month in terms of who has the boys and that is all. I deal with medical appts etc and always notify him once its planned, i also plan this on my time as its impossible to coordinate with him. But your right the less i respond the better, he should get the point.
For me working together means that both of us are aware of what happening in a timely manner, thats it. It doesnt mean that as soon as i have booked an appt i need to ring him and discuss with him.
We are moving in the next 2 months to a much smaller house that will be mine and the boys only, i cant imagine he will allow such behaviour, but yesterday i couldnt wait for him to leave.
In terms of abusive messages, its mainly name calling, “you are nuts” “ are you an actual idiot” words along these lines, these are the most recent ones that spring to mind. In the context of cery long txt messages, often telling me what to do.