Viv - I know you said you didn't ask for enlightenment but very similar reasoning as to why abuse victims stay even though they've experienced some awful things. It's just very difficult to extricate yourself, to diminish that hope that things might improve and doesn't get easier until you reach that final point of no return. This doesn't necessarily get triggered by leaving. It takes an average of seven attempts to leave an abusive relationship. It is even harder to leave after going back to give somebody a second (or thirty-fourth or whatever) chance - it feels as though everybody will say "I told you so". But understand that if you have not mentally reached the end of the road with the relationship, it does not necessarily feel like an escape to get out.
OP - good that you've done bits of the FP online :) Do you feel able to continue it? I started the online one recently although I feel like I fully understand my experience of abuse now, because I recommend it often enough on here I thought I might as well see what it's like. I am actually finding it tougher than I expected, so understand if it's hard going. If you prefer something more passive rather than requiring so much input from you, it would be well worth buying one of the books. Either Pat Craven's book Living With The Dominator (she also wrote the Freedom Programme so the terms etc will be the same) or Why Does He Do That by Lundy Bancroft, who is excellent too, if you want another perspective which doesn't repeat stuff from the course.
It sounds as though you still feel responsible for him? Are you the only person that he has to rely on? Perhaps you struggle with giving absolute nos - wondering what he will do if you don't help him out. Have you thought that that is his problem to worry about?
I know the feeling of feeling guilty about taking his children. You are imagining how awful the pain would be if somebody were to take your children from you. You know that everybody makes mistakes, you've probably made some imperfect parenting moves yourself (you wouldn't be human if you hadn't!) and you're imagining that if somebody used that one time you lost control and shouted as a reason to "protect" your children from you, you'd be utterly distraught.
In fact it is very unlikely that he is feeling the same as you would be feeling in the same situation. Of course he probably is feeling very sorry for himself - he had a nice life with a wife and children at home and now he has lost that. But do not be fooled that he is missing the children as much as you would. Men like this in fact rarely do. Do you not think that if he was missing them so terribly he would be doing everything he could to try and make sure they were happy, safe and cared for? Like not taking money from their mother, for a start.
He is still not taking responsibility for what has happened. His comment that you "failed to include the circumstances" is classic. In what circumstances does he believe abuse is acceptable? In what circumstances do YOU?