Is it permissible to supplicate against an oppressive father who harms the mother, while still treating him kindly and serving him?

It is not permissible to supplicate against one's parent, even if they are oppressive. Rather, one must be dutiful to them and associate with them in kindness. Supplication should be made for their guidance, and one should say: "O Allah, guide him. O Allah, protect us from his evil. Allah is sufficient for us, and how excellent a Disposer of affairs."