The problem with staying in a marriage that is dysfunctional, unhealthy and the other spouse is not making any substantive improvements in the relationship is that the children grow up not experiencing what a normal childhood and loving home environment can be. Even if they as children decide they want a happier adulthood, there's real risk they will end up choosing someone like mom or dad. Do you want them to marry an appeaser, an enabler? Or marry a controller, an emotional dictator? Neither extreme is a good choice. So then, how can you
gift them a more balanced childhood?
Living in a calm and stable home, even if only for part of their lives, will give the children a better example of normalcy for their own future relationships. Staying together would mean that's the only example of home life they would have known — discord, conflict, invalidation, overall craziness, etc. Over 30 years ago the book Solomon's Children - Exploding the Myths of Divorce had an interesting observation on page 195 by one participant, As the saying goes, "I'd rather come from a broken home than live in one." Ponder that. Taking action will enable your lives, or at least a part of your lives going forward, to be spent be in a calm, stable environment — your home, wherever that is — away from the blaming, emotional distortions, pressuring demands and manipulations, unpredictable ever-looming rages and outright chaos. And some of the flying monkeys too.
Yes, this is the exact opposite of what you wanted, to hold the marriage together at all costs. Fact is, the only way to do that is to be compliant, appeasing, enabling of the demanding spouse. And that's not a good example for the children, the cost is too great. Yes, we don't want to dash our dreams and hopes but we do need to face the reality. We can do only so much before we have to admit it just isn't working.
Exiting an oppressive marriage is a horrendous ordeal but afterward the sun shines again.