I love it when Snape lives, especially so ingeniously. The Albus/Phineas section is inspired (PN in particular is in fine voice -- When did you, the pleasure toy of Grindelwald, the randiest Gryffindor to grace the halls until Septimus Weasley began to sow his seed, become such a ninny?" [hahaha]).
And of course, Severus/Minerva, one of my favorite guilty pleasures -- I love her self-awareness and her understanding of his situation. "Good lord, man, how could ye stand it all?"