So based on your updates, the practical issues are childcare and pay.
First off you need to look into entitlements you could get whilst single. Eg: discount on council tax if you're the only adult in the home. Child support? I'm not clear, do you have a child with him too or just your ex?
Look into all the pracalities. Make sure the money you earn goes to a private account (not joint). Consider a second, flexable job maybe. Eg: take up cleaning. A couple of hours a week helping someone woth their house could net you an extra 20 quid or more. And chances are they will be flexible as to when you can go.
Or maybe you have a skill you can use to teach? Or you could make things to sell on etsy (if you're arty). Or sell things on eBay that you don't use anymore.
Basically, start padding out your bank balance.
Could your ex take the kids more often?
Could you move closer to family? ( assuming they aren't toxic too, which may be possible considering you are dating someone toxic. It may be all you've known).
Look to downsize as much as possible. Consider cheaper areas to live ect...
Speak with women's aid too. They may offer helpful advice you hadn't considered. Also echo doing the freedom program.
Start taking practical steps. It may make it easier to emotionally break away when you feel more secure with doing so.