UPDATE!
I got myself lost in all of the setting between the Netduma and my Xfinity modem. I ended up screwing with all sorts of settings and had to backtrack. I was also convinced I needed to set up a static IP, so thank you Crossy! I went back to the links and followed them step by step and turns out I needed to set up the DMZ.
NAT now reads OPEN.
I was initially having "lobby not joinable" problem but seems to be fine now. I'll report back if any other problems arise.
THANKS for all your help!