You can petition the court for guardianship if you can prove that he is a threat to himself and not able to take care of his personal affairs. You will need significant documentation from medical staff and witnesses about his bathing, medication and failing to follow the doctor's orders.

From the limited information in your post, it does not seem that his life is being threatened, and the court will have difficulty awarding you guardianship on that basis. If he is not suffering from any mental defects and is merely being stubborn, you may wish to just try to help your father the best way that you can. Visit, and have family visit him often to check up on him, and possibly contact a home health company to see if there are any medicare or VA benefits that are available to have a nurse or CNA visit your father. I definitely would not give up, but getting a power of attorney may be premature at this point.