i didnt get why ur worried about the reason of his mistreat , trust me it dosent matter why i dont want u to hate ur dad but he's old and it needs a big effort from ur mom to change him yall have to be patient , i suggest u can talk to him using religion, islam only supports peace and kindess especially to your family,  convincing him to seek help from a therapist gonna make it worse generally north africans got so much complexes and issues due to life conditions my dad is so toxic child abused me but i can only forgive him and try my best to change him