No lashings from me...document everything and get something in place to stop this crazy nonsense. Have you given any thought to meeting him in a public place for pick up and drop off of the kids? Is there any way that the kids can meet him in the driveway and you stay in the home? Keep your phone on you at all times when he's around and be prepared to call 911 if he blocks you or does anything in a threatening way. Clearly he's not rational and I'm afraid he's going to harm you in some way.
He needs some down time in the local jail. It just might cool his jets. He's really walking on thin ice and he feels entitled as well as playing the victim game. As for the girlfriend...why is she riding along w/him to pick the kids up? Could this be his way of having a witness if something goes down between the two of you or possibly she's there to give him moral support for his crazy bs? Please be careful what you say or do in front of that woman.
I'm glad you didn't switch weekends. BTW, if he's terminated from his job, how is it he working this weekend? Is this a part time job that he's not paying taxes on, i.e., under the table deal?
I'm very sorry he's still acting out. Please be careful.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.