How can one get rid of hatred and disrespect towards one's father, and overcome the persistent sadness that affects the marital relationship?

You must advise your father and remind him of his responsibilities towards himself and his family, and vary your methods of advice. The wife must fear Allah regarding her husband, and not burden him with her family's worries. She should be grateful to him and treat him well. The children should treat their father with compassion, mercy, and kindness, even if he is abusive, following the example of Ibrahim (peace be upon him) with his father. Sadness should not hinder you from your work and obedience. Be diligent in supplicating for protection from worry and sadness, and for the removal of sorrow and the departure of anxiety.