Is it permissible for two sisters to leave the home of their elderly father, who mistreats and harms them, and move to live with their mother or brother, fearing for their lives and safety?

You and your sister have the right to stay with your mother or brother in a safe place. You are not obliged to stay with your father if you are adults. However, his abuse does not negate his right over you. Therefore, you must honor him to the best of your ability, such as enjoining good and forbidding evil gently and wisely, and helping him to repent and become righteous.