Look, while my neighbour was abusive, constant fighting for other reasons is not good either.

If they grow appart, they might co parent and divorce. That way they would teach their children how to split up amiably. But I don't think it is good that they remain married because it breeds resentment and is toxic.

The scandinavian way (similar to the spanish) is good. Of course, for that to work, both parents need to be mature and learn. But here I blame more the economy than couples. I mean, houses are expensive, you can't always afford to reject a job. And sometimes that means moving away. Inf act I would say that some marriages fail due to external presure (from work and not having enough money), while other relationships (like mine) benefit from having money to reduce discussions (like paying someone to do the cleaning which neither of us like XD).

As for children, I think you should give them credit. Childs are intelligent, they do know what they see and hear. They end learning what happened between their parents. If one is abusive, they will know and resent it. If one cheated, they would end knowing (they might forgive this or not). They know if a parent cares for them, treats them well and is fair. If a child doesn't have high regard for a parent, it is usually because said parent has failed them in some way. In that case, instead of blaming the other parent, you might want to mend the relationship with the child. Listen, try to understand the child's feelings and try to heal the relationship. Don't take for granted that child "owe" things to the parents. If you take care of them and show them love, it won't matter what the other parent says, they would know you love them and reciprocicate. You don't need to be married for that.