Hello,
thanks for your feedback!
I indeed am a big fan of the Theme of Simon

But that's not exactly the reason why it's in there more than once. Do you know Pascal van Stekelenburg's original arrangement of Bloody Tears? It's a real classic:
http://www.youtube.com/watch?v=Bj8V_Ky-kxoHis arrangement is "entangled" by a fragment of Simon's theme, so that should explain a lot

About Death Fair, AFAIK Konami made a mistake and exchanged the titles of the two pieces in one of their soundtrack collections, so that's why many refer to stage 3 as 'Darkness' whereas it's properly called 'Death Fair'. Also kind of makes sense - The second stage was a dark cave and the third stage was a Death Fair in the truest sense of the word haha (one of the hardest Castlevania stages I've known). The Game Boy CVs have a lot of underappreciated music imho!
The Ninja Gaiden Medley sounds interesting, I would indeed love to hear it as well

About sheets, most of the video is played by ear, so there are no sheets. Making a score would also be kind of problematic since in two fragments I used arrangements from other people as a basis, so I would need to get their permission first. Don't expect sheets anytime soon, sorry

Many greetings