Hi Yankeegirl,
I am so sorry to hear about your Dad. My own Father passed away on March 4 of pancreatic cancer, and I can relate to a lot of what you write about. My Dad was also very depressed after his diagnosis, and before he got on better pain management, was absolutely miserable to be around. I felt like I needed to spend time with my Dad as he was dying, but at the same time, he was being such an A-hole that I didn't even want to be around him. So I do know what this is like. Unfortunately, I don't have any answers for you. :-( No matter how much you want to, you just can't change the way a person behaves.
All I can suggest, is to "sweep your side of the street". Do the things that you have control over. Don't feed off of his behavior, be as pleasant and as positive as you can. Know that you are being kind and considerate, and that any negativity is coming from his "side of the street". But protect yourself, know when you have to leave or when you just can't be around him. It is a horrible position to be in, and very emotionally draining. I hope that makes some sense. It doesn't mean you love him any less, just that you won't allow any emotional abuse, intentional or not.
You are not alone....... NiteLad