Static IP - Still getting Connection Refused on my service

I've been trying to get our Static IP configuration working for weeks.

Right now, I *think* I have my Comcast router set up in Passthrough mode (not Bridge) and the phone reps claim all the static IP configuration is correct on the Comcast end.

HOWEVER,

I have mapped a port into my server, port 80 for just basic web server activity, and it gets Connection Refused from outside my network, but of course works fine inside my network.

The reason I think this is still something on Comcast's end: I have tried to rule out EVERYTHING on my own equipment, replaced routers that were totally fine, rebuilt the OSes, all the things. I cannot get this to work still.

I am really frustrated with the phone technicians because they claim they can't answer my questions about COMCAST'S equipment because it's "past the demarc" like, no. This is really really basic configuration needed and Comcast's deploying their Static IPs in the *weirdest way* I've seen in 15 years of doing tech work for small businesses.

I am forced to have to use this COMPLETELY UNDOCUMENTED router of Comcast's which is CLEARLY buggy (settings will revert after you are sure you had them turned on), and Comcast won't even tell me how THEIR IP SETTINGS are supposed to be configured.

This is as basic as it can get for a small business. I'm just wanting my web server behind my static.

PLEASE HELP.