Wow.... I thought I had it bad.... but let me tell you something right now: you are not worthless or at fault. I know the outright rejection. It's not a matter of what you do or what you could do. With that... and I know because it's my family that's done it in a way to me as well... but with that level of outright refusal, nothing you can do will make up for it. I'm sure it's not a matter of what you've done. In fact, just from that, I can tell you straight up that you've done nothing wrong. Your Dad is... well, anything he blames on you is probably something else that he can't accept or focus on, so he's using you. I'm sorry 'bout that.... but, please don't let that make you feel like you have no meaning and are at fault. You aren't. You are you, a person. A nice person, at that.
And, while I don't know what it's like to lose a sibling, I can tell you something, even if it may not be something you wanna hear: someday, maybe not now, but someday you'll get the opportunity to meet him. Don't lose that hope. But... don't try and force yourself into that situation. Your dad clearly seems to be going through something himself, and, as much as it pains me to say it, you shouldn't be around him like that.
I dunno if anything I can say can help, but.... if you need to, I'm always here ya know. You don't have to face stuff like that alone. As I said, I dunno how much of a help I could possibly be, but, I'd try.
But, on a sobering note (because I don't really know what else I wanna say atm)... I've been told of a little party you intend to throw for Kanda~ Heheh.... I like the idea.