The fact that he left without explaining to his children tells me a lot about his character.
My own father left he also never explained, left my poor mum to do it. I’ve never forgotten that he didn’t explain to my face and now don’t have anything much to do with him.
Be prepared at this stage for a lot of nasty stuff from him and his family. Unfortunately relatively OK people seem to do this at divorce.
The advice I would give, having been through this, if it’s worth anything - is it’s really worth forgetting about all of those nasty words. They mean nothing, absolutely nothing. Don’t get sucked into ‘them’, and don’t encourage your own family to side either.
Instead centre absolutely everything on what is best for you and the kids - and I mean everything. He phones wanting to come last minute? Check to yourself, is this what’s best for me and kids. If not, don’t do it. Don’t do things in response to his or other people’s opinions. You will have a LOT of opinions, influence, him having a go or whatever.
It’s just noise.
Starting from today, you at least have him leave the house and you are there with the kids. He hasn’t hung on being horrible. He isn’t trying to kick you out. That is all a good thing.
So from today grieve and get care. But carve those pumpkins yourself with the kids, have a lovely Halloween, immerse yourself with your children as they are your primary relationship and they will give you more joy than you can imagine.