As I'm sure you read in the wiki, file transfer is pretty buggy in Adium. AIM file transfer is apparently greatly improved for the next official version of Adium (currently in beta stage).
Looking at the pic of your router's ports, it seems to be set up properly to my knowledge, the only possibility is that 192.168.2.100 is not your computer's IP (you can check in System Preferences -> Sharing)
Usually, if I'm having issues with file transfers, I can restart Adium, and it will be ok.
Right now, the user I'm sending to will get the prompt, accept, and their screen will say I cancelled the transfer. Mine will say they cancelled or have the candy cane progress bar until I manually cancel.
As m2e said, the beta of Adium 1.0 has a more stable file transfer implementation (it fixed all of my personal problems with it), but it is pre-release software, so keep that in mind.
If you're comfortable with it, try 1.0. If you'd rather wait, I'm sure it'll become an actual release... "when its ready"