How can a final decision be made with one's wife and her family after suffering from their harm and the wife's dereliction of her marital duties, and his certainty that her family has performed magic on him, along with his feeling of intense hatred towards them?

The husband is the decision-maker in his home, and it is incumbent upon the wife to obey her husband in what is right. Her obedience to him is more obligatory than her obedience to her parents. If the wife's family is corrupting her, the husband has the right to prevent her from visiting them and to prevent them from visiting her if they cause harm. It is advisable to treat the wife with kindness and not allow corrupting interferences, and to rectify the shortcomings of the wife through lawful means. It is not permissible to accuse the wife's family of sorcery without evidence. If sorcery is indeed found, its treatment is through lawful invocations (adhkar) and ruqyah, and reliance upon Allah.