The reason I asked about prison, and whether you worked full time, etc., was if he's been to prison so many times, then he obviously has a police record, presumably violence was involved? If he has a record, the police are far more likely to take an interest, so sorry for all the questions, but can I ask, have you actually reported his behaviour to the police, and if so, when, what for, and what reaction did you get?
As for your job situation, it seems that your family don't offer you any real support, so the fact that you work full time, and are used to paying for child care, again puts you in a good position, and while I know it would be hard, it would be easier than living in fear as you do now. My solution - get a new job well away from where you live now. Once you've got something suitable, look for accommodation, I would imagine if you're already on a council waiting list, that that could be transferred. Then once you've got some where, move yourself and your children, and tell NO ONE where you've gone. Not even family, just tell them that you're moving to get away from him, and you're not telling ANYONE where to, but you will keep in regular contact to let them know you're safe - only do this if you don't want to cut them out of your life too. Like I said, I know this would be really hard, but it's got to be better than living as you do now. You could even change your name by deed poll to ensure that he can't find you. In your shoes this is definitely what I would do, otherwise you and your children are going to continue to live in fear for the rest of your lives, and do bear in mind, before you say 'I can't do that', that people do this when they go into witness protection, and for them, they don't usually have time to even make plans.
With this in mind OP, can I suggest that if you haven't already, you join the Women's Aid Survivors Forum. There are other women on there who may be able to give you more advice and help. https://survivorsforum.womensaid.org.uk/