Thank you so much! To be called original is tremendous praise, especially given that we're writing in such a popular pairing (and in the middle of such a huge fest!)
The concept of Snape's curse came directly from the Red Right Hand song; we thought it was something that Umbridge (with her canon fondness for drawing blood from the hand of her victim) might well have come up with.
I'm so glad that the scene where Harry decided to take on the mark of Snape's shame and wear it as a badge of pride worked for you!