Wow. This was so painful, I just squirmed through it, but I also could not stop reading. Your Snape characterization--his ambivalence is so perfect. I don't know if I believe that the Harry in canon would be this awful, but--I believe in this behavior as real human behavior, and I stayed fascinated by it throughout.
I almost thought at the end "Oh, no, he waited so long to grow up that Snape is with Neville and that's why he looks so much happier." Heh!