As for Xkb wizards, there are few such. Not even the xorg devs really understand it that well! See http://www.charvolant.org/~doug/xkb/html/index.html (although it seems to not be responding for me right now). It's a bit of a crawling horror, which nobody really understands (else they would have sorted out this mess, since they've known about it for something like ten years) and everyone is afraid to touch. That said, the basic solution is to use that web page as a guide, copy the Xkb keymap definition you're using and remove all the numlock-related parts. (Unfortunately, that may be easier said than done, given the mess that is Xkb.)