Re the WAN IP changing:
You can tell (relatively easily) in two ways:
1. Once you've started a Halo server, bring up the scoreboard and check the server IP Halo lists. (This is your WAN IP. If it's not the one currently set up, then it's changed -- as I'm sure you know )
2. Open the start menu > click "Run" > type "cmd" (without the "") and press enter > type "ipconfig" (into the black w/ white text box you get after pressing enter before) and press enter. The IP listed after "IP Address" is your current WAN IP. (Mine's 192.168.1.2, for example)
No, I'm afraid that you're wrong: The latter method given will NOT give a WAN IP behind a router/firewall device. (90% of users these days....)
In fact, saes: that IS NOT YOUR WAN IP ADDRESS either! (The entire 192.168.x.x range are ILLEGAL Internet addresses and by rule are NOT allowed to be accessed to/from the Internet directly!)
Blizard: you need to do as I walked you through before: You need to log in to your router device and find that page with "WAN Status" (or whatever it was called) that has info like "Gateway," "DNS Server," and "WAN" IP addresses on it. If you can't find it, PM me and I'll try to find your device's manual again....
>sigh<But if you can get SOMEONE ELSE to join your server THEY can tell you it's IP address once they're in-game, which might be a LOT easier....