go into the router's setup pages,
there's an option under LAN to enable UPNP, don't forward any ports to start off with, save the settings and restart the router, then try connecting to link with the xbox, try getting away without using port forwarding (its should work with UPNP enabled without the need to create specific rules)
the Thompson routers tend not to play very well if you inadvertently cross over port ranges even when forwarding all to the same device
just because your paranoid doesn't mean they aren't out to get you
