He will never go without making an unbearable atmosphere for the DCs. And will make my life utter hell.
Isn't that what he's already doing anyway Hope? I would suggest that if you have any money at all, you take it and put it in an account in your own name.
Use it for food for you and the children. Let the bills come. Let them cut off the electric, the wifi, everything. At some point he will either shift his lazy arse into a job (any job) or realise that his free ride has ended and will move out.
When you feel up to it, see a solicitor with a view to a split. You cannot carry on like this. Everything will be so much better for you with him gone. Your home will be a haven and you can start to build a new, mutually respectful relationship with your children.
It sounds like your 'one day' has come and that's actually a good thing. Start a thread in relationships under a different name to get lots of support and good advice.
But for now just start with the small things. Look after yourself. Stay in bed if you want but please try and post so that we know you're ok(ish) x