I still see the same problems as well. People are still being disconnected after they enter the game. I have placed my server in my LinkSys DMZ to see if that helps. The only other thing that I could possible do would be to remove the Linksys completely and go direct to the cable modem, but I will not go that route. Safety is more important.
I think that since the game is so new, patience might be the best answer and a future patch might resolve these issues. When I ran a JK2 server, I don't believe I started dedicating until after the second patch.
As for the wireless router configuration, technically, you should be able to connect via LAN to the server because you would essentially be on a LAN. However, I am not familiar with the configuration settings of a DLink. As long as the ports forward to the correct address, it should work.
I am sort of confused though...which machine are you attempting to run the dedicated server on (PC or XBox)? Also, does the XBox also connect wireless or is it direct?