How can one deal with parents' unprovoked hatred and harshness, and their physical and verbal abuse, and what are the ways to nullify this sudden change if it is the result of a magic of separation, to restore family relations to their natural state?

This is an unusual and astonishing matter, because typically parents have compassion for their children. We advise you to be patient with them, to supplicate devoutly and humbly, to try to understand the reasons for the change in their treatment of you, and to find excuses for them. If no ordinary reason becomes apparent, the matter might be extraordinary (sorcery or the evil eye), in which case you should perform Ruqyah (definition) Shariah.