Hi dementor,
The listenserver.cfg file is for normal hosted games the ones you do in the Nightfire Multiplayer menu. It's not important to have it to host a game and is not included in the Nightfire install. If you want to add extra commands like mp_spamdelay 2, ctf_autoteam 1, mp_chattime 7 .etc for every new game you play you can make a listenserver.cfg in notepad and put it in the bond folder.
The no IPX is to stop Nightfire looking for it at server start up. If you use IPX networking you can remove it from the dedserv.bat file. NAT menu/edit game files/edit dedicated server "-noipx" As Zero says If you don't you don't need to change this. It won't stop you from connecting to the gamespy network.
To test to see if your server is on line or not you can go here
http://www.009.web-fun.net/test/nat-test.php
If your server does not show up you can use the troubleshooting guide on the same page.
For your router there is a link to a router help page that has almost every make and type of router on the market and how to set them up.