So your PC that's acting as a router is really acting as a NAPT gateway, and port 80 on your router is forwarded to port 8080 (GlassFish's default HTTP service port) on your GlassFish server box? And GlassFish is listening on port 8080 of that box?
If that's the case, then you should be getting a page served from GlassFish when you connect to port 80 on the public IP address of your router and issue an HTTP GET. If you're getting some sort of page served by your router, then port forwarding is not actually working on your router. Do you have some sort of HTTP server software package listening on port 80 on your router? Is it possible that that HTTP server is reserving port 80 and your NAPT gateway code isn't able to override that to forward those connections over to your GlassFish box?
Or maybe you forwarded port 80 to port 80 (instead of 8080), and you've got your OS's built-in HTTP server running on port 80 of the GlassFish box, and when you connect to it and get the default generic "you haven't set up your webserver yet" message, you thought it was coming from the router PC when it was actually coming from the PC you're running GlassFish on?