What can a son do to end his father's insults towards his mother, who has repented, and to resolve the disagreements with him that have reached the point of estrangement, as well as to solve the problem of his refusal to allow him to marry a committed woman who has been previously married?

Allah has commanded kindness and dutifulness towards parents. Therefore, it is not permissible to abandon one's father or treat him poorly, even if he has mistreated the mother. Part of being dutiful to the father is not marrying a woman whom the father rejects. The wife has a right to a separate dwelling. It is forbidden for the father to curse or harm the mother, and he should be advised gently and wisely, seeking help from those who can influence him.