Stay calm Wombat, just like your spirit animal. This is just one small step towards separation and divorce. Don't get sucked into tit for tat - the kids will eventually work things out themselves.
I can see that when he finally engages they would be so grateful they will temporarily overlook everything else that has happened. Just keep doing what you do, which is be a rock for them.
It might pay to have some time alone with him, sober, to make the decision to go ahead with the divorce and agree on some rules regarding what you tell the kids. At the moment it's just stringing out and causing everyone extra stress.