If you watch old episodes of intervention a divorce in someone's childhood occurs in 80% of the episodes. This gives you some idea of how traumatic it is for a child to experience. Yes; parents can do a lot to mitigate this and many parents really try but its almost impossible for children to see their parents as two separate people who lead their own separate lives before forming a unit. They see something whole breaking a part rather than two separate pieces disconnecting. The evidence of trauma can be seen in Sabrina's reaction to her father's new girlfriend.
Its always strange to me when STTW mixes more dramatic themes into it's magic universe. There's nothing funny about domestic violence and there's certainly nothing funny about imagining how it goes down in the other realm.
This is isn't a bad episode by any means but its just a little, I don't know... stuffy.