I wasn't able to get it to work, so I just made a Google Cloud instance and put it on there. It works up there. Not sure if it was something about running it on Windows, or something about Comcast not wanting me to serve web traffic from a personal IP address.

No.

Additional points of clarification:

4) There are other servers, such as Plex, on the computer that can be connected to from the internet

5) I was able to curl the root page / from the router and successfully get the logon screen, with and without SSL enabled.