Good gawd woman, when you venture into Angst you jump full in don't you! And while the story was full of angst, I don't feel it was to the point of over done. While, I would have liked less, that is simply a matter of taste. It didn't feel like you were inventing things, just to keep the stress up. Everything had it's place, and that in turn crteated more power in the end.
Amazing story, more twists and turns than the Vortex. (King's Island Rolercoaster, for those that don't know) For the longest time I was convinced that something Albus did to protect Severus in the end was going to end up killing him. But your ending was much better than my imagined one. I feel bad for the castle, because in the end, it really did lose it's Champion.