As a fan of both anyone-rescues-Harry-from-the-Dursleys and evil!Dumbledore fic, I enjoyed this. Very nice to see Flitwick as a major character and your OCs are well-fleshed and likeable. It's interesting to contemplate what happens in this universe with Harry and the prophecy; I think you've sown some seeds with Harry's early control of magic and being raised by dueling champions. I'd have liked to see more of the mentor aspect, I think, but since I enjoy a good Snape-fic regardless of Harry, this was fun.