What are the limits of honoring one's parents, and does the principle of "You and your wealth belong to your father" apply to the case of a son who fears that his stepmother will take control of his money and his siblings' money, especially since the father does not provide for his younger children, and the son seeks to please his father without violating Islamic law and while securing his siblings' rights?

Allah Almighty has made it obligatory to honor one's parents and be dutiful to them, and He has forbidden disobedience to them. He has linked being dutiful to them with His worship and gratitude. You must strive to please your father so that you may enter Paradise, and give him money if he is in need, because the Hadith "You and your wealth belong to your father" means that it is permissible for the father to benefit from his son's wealth, not that he owns it. As for the land on which you built your house, if there is no proof with legal documents that your father gifted it to you, then you do not own it merely by building on it. Rather, it is considered a loan (ariyah), and in this case, if your father wants to reclaim it, you only own the value of the building as scrap. Therefore, you must satisfy your father and be dutiful to him, and try to persuade him to spend on his other children. Be diligent in performing ruqyah (Islamic exorcism), and avoid accusing anyone of sorcery without clear proof.