Is it permissible to prevent a father from marrying a woman who practices witchcraft and grave sins, for his own good and the good of the family?

It is not permissible to accuse someone of practicing magic and sorcery without clear evidence. If you are certain that the woman is committing these forbidden acts, then you must inform your father and dissuade him from marrying her. You are permitted to take the matter to the judiciary to prevent and deter her. As for your preventing your father from marrying, the meaning and method must be clarified.