What does the Torah say should be done in the case of an abusive parent? Sorry if taboo or triggering

I enjoy learning about psychology and psychiatry, and a YouTube video was recommended today about abuse. It’s such a messy topic on its own that adding the layer of Jewish culture and religion makes it even messier.

What is the Halachah for an abusive parent?

Does someone have to follow that 10 Commandment of Honoring one’s Father and Mother? How much?

How does it work connecting with one’s community?

What happens when that parent dies? Does the child have to mourn them?