Goog job! This extension saved me in my wiki project. I have customized on category with incorrect sorting. Now everithing is perfect → http://prntscr.com/6w0jet
Topic on Extension talk:CategorySortHeaders
Glad it was useful to you.
Alas, I wish that mediawiki did natural number sorting, and grouped digits as 0-9 out of the box (In theory possible without to much trouble using ICU library, but nobody has really looked into it).