Is the father of the girl lawfully entitled to keep the dowry after the annulment of the engagement to the suitor who falsely accused her and her mother of sorcery?

What this person did, accusing you of sorcery without proof, is forbidden, because it harms Muslims and is a false accusation, as Allah Almighty says: (And those who harm believing men and believing women for [something] other than what they have earned have certainly borne a slander and a manifest sin.) And the Prophet, peace and blessings be upon him, said: "Whoever says about a believer something that is not in him, Allah will house him in the mire of putrefaction until he recants what he said, and he will not recant."

As for the jewelry, it is the right of the suitor, and you must return it to him. Your father's insistence on punishing him is not correct, but you have the right to report him to the competent authorities for accusing you and defaming your reputation.