Connecting to the masterserver is an outgoing connection, no need to forward anything, but your firewall(s) must not block traffic on the port in question, 29339 that is.
Regarding the whole "why can people connect from the list but I can't?" thing, it's because when a client requests host information from the masterserver, what it receives is obviously the external IP of that server. The client then attempts to connect to this IP address, which the router may or may not handle as expected. The expected behaviour is for the router to "know" that it itself represents the node requested, but also knows that the true intention is to connect to the server behind it.
This can be achieved by enabling NAT loopback, a feature supported by the majority of modern routing hardware, though not enabled by default and often not accessible via the web configuration panel. Use SSH/Telnet to connect to the router, instructions on how to find NAT loopback can certainly be found on the intarwebz, or, if it's a good router, in the manual