Is it permissible to serve the husband's father and change his clothes while his wife, who mistreats him, is present? Is it right to refuse to do so? What is the ruling on the husband's stance regarding his desire to serve his father in order to preserve his feelings?

It is not obligatory for the wife to serve her husband's father or mother. However, it is good for her to serve her husband if he needs it. If that is not possible, his male children must take care of their father; otherwise, they should hire someone to serve him for a fee. If all of that is not possible, and the wife or someone else volunteers to serve him, then it is permissible due to necessity, while being careful not to touch the 'awrah with the hand and sufficing with covering, except in cases of extreme necessity. A doctor and those in a similar position are permitted to look at the 'awrah when necessary, and it is estimated according to its necessity.