I'm so glad you liked it! Thanks mucho for the kind words. You deserve a lot more smutty tribute than this.
Honestly, the fingers/cock bit just sorta hit me as I started writing it; no idea why I never thought of it before, but it's definitely going in the repertoire now. I think you inspired me. :-D
James/Severus seems to be the only pairing I can write hate!sex for, but maybe I'll start stretching my limits a bit in that area.