You're stuck at the moment in what I call 'doom scenarios'. You can only see bad outcomes from the decision to leave - mostly to do with the children - and they are occupying all your thoughts and negatively affecting your confidence in your decision.
Whenever you take a big decision, there will always be something that goes better than you expected and other things that will go worse. There is no risk-free decision so trying to eliminate the risk is not possible.
I'd suggest you have to assume that your children will cope with new schools, new homes, less access to Dad than currently, less money, whatever. Children are very resilient, you do your best as a parent, and whether they grow up hating or loving you is not something you can realistically control. So park that concern under 'pending'
Then pare it down to the crux of the problem ie. the relationship between you and DH. You paint a picture of someone very uncaring, selfish, rather aggressive and unpleasant. Is that what you want or not? Not what your parents want or he wants or the kids want.... is it what you want for the next 10, 20, 40 years?