Hey brutha, we all need to get things off our chest every once in a while. Keep you chin up and remember, you Dad will always be your dad no matter what. Have you looked into disability pay for him? If he is anything like my dad, he would rather be raped to death by a Blue Whale than file for disability, but roofing and such (pretty much the same thing my dad does) couldn't be good for him right know.
I hope this works out. I have been in similar situations recently (friends getting tore up in Iraq) an it is never easy. The best advise I can give you is to be there for him and make him understand how the people around him would rather have him there with them weather it be with only one finger and two teeth or exactly as he is.