Every time you speak-

I don't think I've ever touched on this subject in public before, but I can't avoid it if I'm going to be completely honest on here about everything that's happening and everything I'm battling.
My dad...he's a good person. A good father. But the pain that he's been going through for so long, it just ravages him. I've been told he had an anger problem when he was younger, but that he had mellowed out a lot with age. Well, I would hate to have gotten him mad back then. I don't want to be mean, cruel, or out of line. But I'm over-flowing. I'm tired of wondering whether my relationship with my father will continue to go back and forth between such extremes, for how long, and really, how long can this continue before one day, it just crashes and burns into nothing but ash..? The horrible part about all of this is that sometimes, in the heat of the moment, or when I've had enough of being yelled at for nothing, just because I'm there and my dad's in pain, I think to myself how I don't even care if it doesn't get better. I think to myself, one day I'll just walk away and never come back, never even look back, and he'll be sorry he treated me like his whipping boy.
I know that I think these things because of all the pain he causes me, that I just want to cause him pain too, but the fact that I think these things at all makes me feel so...horribly selfish. I KNOW he's in so much pain, okay? I KNOW. I can't imagine the level of pain he's in constantly, how its just getting worse, and how even sleep now evads him-his only respite from everything. And when I put it all out in front of me like this, it seems even more selfish that I am so sensitive to his every word, his every look. But the way he talks to me, it's like he has no respect for me at all. And sometimes-I swear to God, I swear on my life may God strike me down, he treats his dog better then me.
I know no one will believe that, but it's true. My dad's anger over the years has funneled into a concentration of fury, which is now aimed solely at me. I'm the bottom of the funnel. I bear the brunt of his anger, and some days, it's almost enough to kill me.