It is a crazy amount of gymnastics just to deal with them.
And the more distant they sense you're getting, the more they try to reel you in. They'll alter tactics trying to find something that will work, and unfortunately frequently that includes escalating the abuse as well.
I see it like this: When you were in that relationship you were tied together by a number of feelings and circumstances. You're trying to untie that rope. He is tugging the rope to see if you're still there, and as you don't tug back, he's yanking it harder and harder and harder to get your attention.
Emp919, what worked for me: Calling his bluff. The police probably won't protect him (they hear this crap all the time and it's usually crap), do not hesitate to get the police there to breathalyze him or otherwise get a feel for his state of mind before he drives off with your kids and get some of this stuff on record in case you need it later (it sounds like you might), and do whatever is necessary to NOT get yanked around on that rope if you can avoid it. He will see everything you do as an escalation, but try not to be intimidated.
My ex had me so traumatized after we finally split that I had to do some PTSD therapy afterward just to keep my footing whenever I dealt with him. There's no shame in needing it if you do. :ghug3