Is it considered a form of undutifulness if I do not go to my mother, who accuses me of hitting her, knowing that I believe she has run away without just cause? And what should I do about my wife, who refuses to live with my mother due to her behavior?

It is not permissible to abandon one's mother or stop visiting her, no matter what she does, for that is an act of disobedience (to parents). The wife has the right to an independent home, and this is not considered an act of disobedience to the mother. Similarly, it is not permissible to deprive an heir of their inheritance.