He even spoke to dc last night and tried to justify and get them onside
By 'onside', I assume he's trying to convince them that you are being a 'bad' mother/wife or similar? If so, this can be considered parental alienation. Where I live (US) it's grounds to lose access and if severe enough, parental rights. Are your children very young, or are they old enough to see through him? As hard as it is, don't 'counter attack'. Just reassure your children calmly that Dad is wrong, you love them, and you want the best for them.
I'm glad you're going to speak to your doctors. Do you also see a counselor? It may be a good benefit to you to have someone to 'vent' to, help you sift through your emotions, and give you tools to cope until you can see your way clear. If you truly feel that your family won't be supportive of you, a counselor will be invaluable.
I know you may not be 'there' yet, but remember that you can file for a divorce even if you're living in the same household. It may be a good idea to see a solicitor for an 'information gathering' session. It does not mean that you have to file anything and if he's that much of a jerk it may not be worth the aggro until he's gone. It just means you're educating yourself as to your options and what you might expect in terms of maintenance and/or settlement.
I agree with above PP who says to stop providing 'services' for him. And if there is a spare room, move into it. Begin to think and live as a 'single mum'. You'll be one soon (O, blessed hope!) so you may as well start figuring out how you're going to do things, anyway. Try not to engage with him. But if you must, every response to his antagonism/insults should be a very calm "I want a divorce" or "If you feel that way, we should get a divorce". Don't respond in kind and never JADE (Justify, Apologize, Defend, Explain). Remember that every time you do, you're just giving him more fuel for his fire.
This is going to be a rough time, I'm not denying that. But as Churchill said "When you're going through Hell, just keep on going!". You've already taken the first step, you've made the decision to live a better life. The rest will come in time.