Is a person considered sinful for treating his father harshly, keeping his wife away from him, refusing to bring him to live with him, and visiting him once every week or two, because the father harassed the son's wife?

You are not guilty in your father's regard, for you were dutiful and benevolent towards him despite his unlawful actions. May Allah reward you for your dutifulness to him. Continue to supplicate for him, seek forgiveness for him, and give charity on his behalf, for this is part of honoring one's parents after their death.