To think this is bad manners?

[akaemmafrost]

Is it rude to walk into a room where someone is sitting reading and open a window wide, without asking the person who is already in there if they mind?

I would never say anything bad about him. I know how important it is not to do that but I do defend myself. Like today I said "Mum wasn't making problems, we just didn't agree about something". Something had to change though .

Has to change not had

I would suspect that he had other plans which didn't involve the DC. So he picked a fight over something so he could flounce off without them. If you hadn't reacted to the window he would have picked a fight over something else I guarantee it.

OP,

arrange to have a neutral friend act as a pick off drop off place, have a hand over book so you can communicate relevant information,

your children do not need to hear anyone talk about their mother like that, or have a parent behave like that in front of them,

He clearly has boundaries issues, remove the opportunities for his issues to infringe on your life.

My exH texts me or one of the kids when he pulls up outside the house and I then get kids ready and off they go he doesn't come In to my home, perhaps this might be a better way to go.