Hmm... Not sure how much of a help this will be, but I think I know a way to determine the Craft DCs.

First, figure out at what level, approximately, you want a character to be able to make a given graft at. Then add 10 to the level. That should at least give you a good place to start in determining the Craft DCs.

Also, awesome work. Kinda reminds me of the Mad Hatter from American McGee's Alice. I'm looking forward to using these for a character.