A. has the right idea. As much as he’ll be pissed off at you, it sounds like it is in his best interest for you or one of your siblings to get a POA.
One of my dear friends went through this with her father, who was also a veteran. He was angry, but he was incapable of tending to his own needs, financially or health wise. Your father’s refusal to apply for VA benefits is disheartening. They are a royal pain in the ass, but he served his country and is due them.
Does he get any VA benefits at all from his service already? Is the VA who he uses for medical care? If so, it isn’t as difficult as he’ll already be in the system.
I’m here if you need anything. I have dealt with the VA A LOT and would be happy to help in anyway I can.