Hey there.. author here\,
SOrry ive been away from this thread so long, been building other sites and had pretty much forgotten about this.
re: further documentation, when I made this, it was only for myself, so I didnt bother to mark any changes in the product_attributes.php file. Mostly the changes are to the HTML of the tabling on that page, to accomodate the new "sort" column. If you do a diff between my version and yours, you should be able to pick out all the small changes.