I've never watched Groundhog Day so no comments there. However, you're cruel, very cruel, for making Severus suffer so much >: D
Despite the pains you put him through, you DID use all the relived days to your (Severus's) advantage, giving him a chance to discover himself (and Harry). Plus, I've always felt slighted by Rowling's blatant dismissal of the Slytherins but you (he) gave them a chance to fight against Voldie. Well done!