LOL! I'm glad you liked it! Or, at least, I'm glad you didn't hate it! And yes, I know that a lot of people wouldn't read stuff with this level of kink, but I wrote it for my recipient, based on her requests. She liked BDSM, so I gave her BDSM.
As for the bloodplay... I debated whether or not to put it in, but really, it was necessary. There are some very intense emotions accompanied by symbolic knifeplay and bloodplay within a BDSM scene. When a person is brought up to that level of intensity, as Harry was in that scene, and is at a sharp release point, it's an extremely intense emotional release, which was exactly what Harry needed. Also, Draco's comment earlier that Harry needed to feel, to cry, and to bleed was as much literal as figurative. It's a huge release-point for Harry in that fic, where he really lets himself go.
I've actually participated in BDSM in real life, and the psychology of certain kink-acts is actually more than some kinksters handle or understand. So, don't worry about the blood-play bit there. Yes, it had a real purpose, both emotional and symbolic, for Harry. I hope that didn't ruin the fic for you.