Seedboxes.cc default settings are already optimal, therefore there is nothing wrong with your rutorrent settings.
For you questions about low upload speed (as per your screenshot) -
Torrent 1 & 4 are uploading at low speed as number of
seeders are quiet high & so not all
peer are just connected to you only.
Torrent 2 & 3 have very low
leecher & they might already connected to another
seeder.
Hope you got my point
btw no
seedbox provider help user in setting up plugins or how to use them, though seedboxes.cc WiKi is one of the best around