Oh my god. This was perfectly amazing; I can't even tell you the last time I enjoyed a story this much, the last time one kept me completely riveted over such a long time (because I had to, like, sleep and go to work and stuff), the last time I cared this much about what was going to happen, the last time I was this torn between the urge to read faster and see what happened and the urge to slow down and savor every word.
I said, "Oh," out loud, in my empty living room, when Snape dropped the herbs on Harry (whispering! god, I could spend a happy hour just imagining what he might have been saying) and again when Harry said, "Is there anything at all you want?"
Your dead Lily is more alive than anything in the books, too.