@yellowflora
I've only read your posts so apologies if I'm repeating others' advice. There is nothing wrong with staying for financial reasons. You just have to understand and accept what you're getting into.
I have a friend in a similar situation. But she's older and her children are grown. Her husband is not a cruel man, her main complaint is that he drinks too much and as a result is pretty much a 'useless lump' from around 11 am on. Every day. She feels somewhat isolated in her own home. Her good friends (including me) live over 100 miles from her and her children are grown and involved in their own lives.
She's staying purely for financial reasons. As much as she dreams of having her own little place (where she says she'd be 'alone, but not lonely') she knows that she'd financially be living on a shoestring whereas right now she has a comfortable life where money isn't an issue. So she made a conscious decision to stay knowing 'it is what it is'.
The main thing she's had to do is emotionally divorce from her husband. She relies only on herself for entertainment and keeping occupied. She relies on herself and her friends for emotional support She does travel to various friends and stays a week or so (and we always welcome her). She visits her DC, although her H usually sobers up enough to accompany her.
Will she ever leave him? I don't know, but I doubt it. She's carved out a life that she's content with in exchange for being able to go where she wants and spend what she wants. All in all, I don't think she's unhappy with her decision. She knew what she was getting into when she decided to stay. Moments of frustration, sure. But for the most part she's happy with her life.
Your situation is obviously different with younger DC, but in the end the decision is the same; to stay when you know you could have an emotionally better life if you left. You are also contemplating moving to a different country, which poses its own problems. Since your DC are under 18, you need to read up on the Hague Convention and if you are currently residing in a Hague country, decide if your H would fight you if you tried to take them to the UK. If so, consider what the chances are of you convincing him that a move back to the UK would be 'best for the whole family'.
It's not an easy decision to make. Either way you make a sacrifice, either financially or emotionally. So just think carefully. And also look at how many years you'll have to live with that decision.