What should I do regarding my father who wrongs me and mistreats me under pressure from his wife, prefers my step-siblings over me, and tries to humiliate me and my wife?

Filial piety towards parents and treating them with excellence is an obligation, regardless of their condition. Even if his wife wrongs you and spoils your relationship with him, and he is obedient to her, you must alert him to the obligation of justice between children and the danger of injustice, but with gentleness and politeness. It is advisable to seek the help of righteous people to counsel him. Responding to a parent's ill-treatment with kindness brings affection and protects against the evil of Satan.