I'd be making him wait outside hun - have the boys ready on time, he buzzes, you kiss them goodbye and close the door behind them.
Your kids don't need to hear this shit. It will escalate.
The fucking nerve - what a little man that he can't keep his kids out of the line of fire.
The sad clown has had these mantrums in front of my girls. Most handovers are done via school drop off/pickup - by design so I don't have to see him.
We had a rare 'in person' handover because my little girl was sick. Now - we've never separated the girls - when this happened before both girls were picked up and the well one was taken to daycare/school by the parent staying home with the sick one. He gets here and tells me off in front of the girls "didn't you take DD6 to school? You could have told me - this is REALLY inconvenient". My big girls face fell - I gave her a hug and calmly said to him "No - this is the arrangement we've always had. If you wanted to change the standing arrangement you need to let me know."
But too late. Damage done. My girls had heard it and my big girl blamed herself. I talked to her about when she came back to m 2 days later but I know she still blamed herself.
I hated him with the fire of a thousand suns that day. Not that it did my girls any good.
Focus on them. Do what you can to keep them out of is. He STBX can't control himself them there are things you can do.
Have you started the exclusive use process? Can you arrange to have a family member, friend or neighbour present when he is coming over? Do you have your VAR on you and recording everything he says?
Yes he is a douchebag for doing this but try not to focus on that - soon enough you'll be used to it and it will barely register. Your kids on the other hand - they do need your focus because they sure as shit aren't going to be hat guys focus.