Fantastic. You've crossed the t's and dotted the i's of canon. (Thank you.) I especially love your incarnations of Minerva -- I imagine her smoking cigars and grin -- and Lily, but all 'round, you characterised everyone wonderfully.
I think I remember reading that this is to be your final Snarry fic, and if that's true, I wanted to:
--thank you for the amazing four you've written; --tell you that you write (in my admittedly insignificant opinion) the most compelling Snape in fandom; --and say that you'll be missed (but that I understand that talking after you've already said your piece is...unproductive).
Fuck, I feel terrible (and like a pretentious ass) saying this, but there are some minor typos. (If you need a line editor, heh, I've got the OCD slant for it.) But seriously, what a marvelous, real, cathartic piece.