Hi e_talis -
First, it couldn't hurt to upgrade to 1.8.3 before you get started again, as it offers lots of new features and a few bug fixes.
As for increasing the number of keywords found, try 1) setting the search depth higher, and 2) making sure all your pages are linked to on your site so that phpDig can find them. You might want to set up a site map with links to the main parts of your site. Just make sure phpDig can find a link to your site map. Good luck.