Many of us fatherless daughters (myself included) see a piece of ourselves in your question. We were once at that critical point, too, where we needed to step back from the situation at hand and ask ourselves: When are we ever going to stop being the poor little girl who desperately wants him to be a daddy even though he's incapable of being one? When are we finally going to stop identifying as fatherless daughters, release that longing, and enjoy the present moment? When are we going to cease re-wounding ourselves every time we think he'll be different?
If your dad still rejects you, he may be too wracked with guilt from being an absent parent and, therefore, doesn't believe he's worthy of your help and compassion. He may, perhaps, have other people in his life to assist him or think he deserves to suffer and die alone. Whatever the case, you need to accept that he doesn't want your support. You need to realize it has everything to do with him and nothing to do with you.
It hurts so much because of its finality--that stone-cold reality that you'll never have a loving daddy. You're holding on because you don't want to give that up and admit the truth. This is the time, though, to adopt “radical acceptance” and find peace of mind.
When my father was sick and dying in the hospital, he didn't want to see any of his children and grandchildren because that's who he was. He was no different in death than he had been in life—stubborn, detached, and unloving. There was never going to be the closure that we see in sappy movies with an “I'm sorry” or an “I love you” or a “Please forgive me.” He denied us his emotions in death like he had denied us his emotions in life.
In this situation, there's more power in letting go than in continuing to hold on. You need to accept that you can't have what you want and move forward with people who love and appreciate you and desire a reciprocal relationship. Take care!