OK, so you seem sure what you want, which is good. Just remain firm and remember why.
Your H has joined the ranks of Twunts, Chunts and Knobheads, of whom sadly there are many.
They seem to have personality transplants, and what actually happens is that first they remove any nice feelings for you and they replace them with zilch, or annoyance or resentment. So no matter what they did, it is all your fault, always has been, always will be. All sense of reason and fairness is also removed, thereby whatever you do will be deemed unreasonable.
He will twist the knife because ultimately he wanted to carry on having his cake and eating it too, but he got busted and you made decisions for him. If this isn't what he wanted, then he shouldnt have hooked up with OW.
Make it plain to him that you will not discuss things with him when he is drunk and then when he is sober, make it plain that OW is welcome to him, that coming back is not an option and that you will be quite happy for him to move in with OW, as long as he sees the DC regularly. That should take the wind out of his sales and confuse him for a bit 