God, that's wrenching. Beautifully written. I still have a hard time believing that Severus' whole life was defined by unrequited Lily-love, but even so, that's how Harry would see him and mythologize him, and the path by which Harry would make his peace with him. Ouch. Ouch. Ouch.
*off to re-read the warm-fuzzy shopping-list fic* ;-) (...even if it isn't canon)