Thanks for the nice clear post. You should get better speeds, though of course you are limited by the hosts serving the file.

Try this 2MB test picture (magnet; just a pic of some sailboats). You should be able to dl at up to 100KB/s http://www.magnetdb.com/viewtopic.php?t=16

Too, you could try a popular file, like "serial box."

Did you turn off Panther's firewall, set up the router's port-forwarding and check the "Force IP" preference in LimeWire?