Yeah, that's a tough situation but I think you're doing the right thing by showing him respect. My father and I didn't have a perfect relationship...there were some bad times. But ya know....while I was taking care of him in the end. That stuff kinda just went away and we became better friends. Each situation is different and yeah...seems like you went through some shitty times. He's your dad and you're his son after all. Even if he doesn't know how to say it...I'm sure he appreciates that you're there for him. Stay strong.