WebDev Module - Possible to change port for HTTP requests

We need to make the gateways HTTP requests accessible without exposing the entire gateway to the network. Is it possible to change the port these requests use?

No, Webdev is just mounted on the ‘main’ webserver on whatever HTTP(s) ports you dictate.
You could stand up a reverse proxy (nginx, Traefik, etc) on the same server as the gateway that listens on a different port and, if the incoming request matches a pattern, forwards the request to Webdev.