Much as you're, on the whole, shocked at what goes on behind closed doors in someone else's home I'm shocked (but not surprised) at the wild interpretation/misinterpretation of some of the OP and projection/speculation based thereon.
I did not say I walk away when h is winding up the kids, what sane parent would do that ? I walk away when h is annoying me when he's had a certain amount of beers. I'm always around for the kids when they're home, h does practically nothing with/for them. I have no social life in the evenings/weekends that doesn't involve being with the kids.
Ds is not being physically bullied at school - He has an issue with 1 or 2 kids being mean to him since term started a week ago (he has a suitably large circle of friends, he is not majorly isolated or anything), it's just a sudden thing that's blown up in respect of a mean kid and their sidekick(s) presumably deciding it's ds's turn to be picked on this term.
Ds did not IME require a trip to A & E as a result of the incident. If I remotely thought he did I would have taken him myself.
The kids and I do not and have never walked on eggshells around h. They take their cue from me and I call him more and more on his bullshit. They also stand up for themselves around him if required. The damage being done is seeing parents who don't love each other in the death throes of a marriage. H would never have moved out voluntarily so it would have dragged on through a divorce which he was always, IMHO, going to contest and drag his heels over in one way or another at every fecking stage but now sadly I have genuine reason to enforce that he lives elsewhere whilst the paperwork and divorce process is in progress.
I asked "has he crossed a line here" because that was what I told him on Monday morning (there would have been absolutely no point in saying this on the Sunday afternoon when he was drunk) and pardon me for seeking a little validation of the phrasing I used when speaking to him before he left on Monday.
He knows he is not welcome back because I have since told him that I consider that I could lose the kids if I allow him to come back into the house after what happened on Sunday afternoon.
I'm very much trying to ensure that the kids don't see daddy having to live elsewhere as their (or indeed my) fault in anyway and it's just possible that ds will feel it's due to him if this isn't handled right over the incident on Sunday. I've read so many accounts of children believing they caused a marriage break-up and how it affected them for a long long time.
Some posters have been helpful in their advice and I thank them for considering the matter carefully before posting.
I, and no-one else, am in control of the situation and my kids are physically safe and will remain so from now on. I now need to work on limiting the emotional damage, assessing the situation to date and reassuring/reversing where possible.
I'm sorry if this isn't drama llama / emotive language overload enough for MN relationships threads but I'm a practical, get on with it kind of woman. Now that I've taken the first steps I'll be following through as I generally do on tasks.