Sorry it's just 9101, I updated it.
In GUI you can change the port of the GUI and that's what I did, so I can right now actually access it using 192.168.1.2:9101 and it works. Do you have NPM configured in anyway other than pointing? have you made any changes in Syncthing itself to give it a domain name or an address?
The forwarding is actually taking place, the problem is that when I write credintials and try to login it doesn't