You can't get a power of attorney from someone with delerium or who otherwise is not mentally competent; only a mentally competent person can grant that authority. What you need to do is to bring a legal action in family court seeking to be appointed his legal guardian while he is incapacitated; because he is not competent at present, you need a court order to grant you the authority you need. Ideally, retain an attorney to help you; if you can't afford a lawyer or wish to this yourself, contact the clerk of the court for instructions.