Hello,
What web address would be used to access the Gateway app from outside of my local network. I enabled port forwarding for ports 80 and 443 on my Pi's local IP address. As far as I know, I do not have a static Ip address through my network provider (ATT U-verse). As of now, I can only access the Gateway from inside my LAN with the following address: (https://raspberrypi2 or https://raspberrypi2.att.net)
Thanks!
you external (router in your case) address. Just like if you had any other http server, in this case it RPi serves this gateway as landing page. Look what IP has your router on network, then go with browser to that IP (if you have port forwarded port 80 like you've said)