Matt,
I'm still pretty much in read mode, but thought I'd chime in, too.
You hang in there. You're doing a great job of being a loyal son, honoring your parents.
I strongly suggest you rethink that "we don't need them yet" idea. You need them now - when things really go down the tubes, you will be thankful you had help and an occasional break. I spent three months taking care of my parents after their accidents with exactly one 4 hour break. Got to hear how nice for me to be "on vacation", too.
Get the time off, it will do you good.
I know it hurts to have him angry at you But that is not them, that is the pain and the injuries and the medications. Same goes for your dad - there's just no there, there anymore.
You're in my prayers,
Panthera