As someone who grew up in a "stay together for the kids sake" home. I can say unequivocally that in our case it was horrible.
We never saw affection, we never learned what a healthy or loving relationship looked like. We didn't learn how to talk to a partner.
We did learn what unhappiness looks like, and that being with someone you didn't like was normal.
We learn how to walk on eggshells. To never ask questions. To never want anything better.
We also learned that children make everyone miserable.
That we were responsible for our parents situation and feelings.
We learned to feel guilty for what we put our father through. Because if we weren't there he would have left and it would have been better all round.
He wouldn't have felt obligated, mother wouldn't have resented him.
They wouldn't have hated each other.

This household was extremely effected by mental health issues, and was far more dysfunctional than yours sounds.
Obviously you work out you can't be responsible for the choices of others. But even at 38 still feel guilty that my parents were so unhappy.

I understand though that it would be a battle to separate. So what I would say is talk to your kids as they grow up be as honest as you can and help them understand about relationships and what they are worth as people in their own right.

I really do wish you all the best. Take care.