Hi--nice job of providing info

Doesn't sound too shabby: -10-20KB/s can be pretty good: 0-1 is often more likely, but varies greatly depending on too many factors to list here, but here are some ideas:

-Upgrade to 2.9.8 or newer, if available, but clean out the old "limewire" files and prefs first (and save the 2.8.6 LW download .bin just in case)
-allow port 6346 (search for "Norton" for more info. I know very little about that firewall, but there'll be others willing to help if a search and your manual aren't enough)
-routers can be a problem: can you provide even more specifics? (you might have to set the Force IP pref)

btw--watch out for spam files (small fast files that show quickly in searches with provocative names, often), and keep them out of your shared folder.
--in the newer versions, automatic requeries are stopped; you'll have to use "repeat search" to build up the list of alternate sources once LW has tried all sources found in your last search)
--try command-clicking and control clicking to discover some hidden features in LW)
--share >100 good files and other machines are more likely to try to keep you connected.

Cheers. Hope this helps for a start