Ooooh, this was brilliant! So wonderfully snarky and slightly evil. I love that Harry's suspicions regarding Snape's actual job are not actually because he's a bit crazy, but because he's good at his job. Also, I really loved the dialogues - the bit with Wiggens was great and I really love your Ron. Like in this part:
"Brilliant," Ron said, dropping his head into his hands. "Out of curiosity, am I still listed as your emergency contact?"
"Yeah, I think so. I never changed it from the first time I filled it out. Why?" Harry said, standing and stretching.
"Can you change it to Hermione? Looking at dead bodies always puts me off my dinner."