MKD,
Your first problem is going to be with the PC running as a firewall for your network. This will only cause you problems and you should really stay away from using a PC with Windows for any type of network appliance. I suggest you go with a well known dsl modem with built-in firewall and switch like a linksys or even a Cisco. Yes Cisco is great at routing, switching and firewalls.
Once you do this, you will still have the problem of the Tenor being on a private IP with a dynamic public IP NAT’d to it. As I explained in my previous email, the only way you can resolve this is that you MUST have a Quintum Gatekeeper or a Quintum product with built-in Gatekeeper on a static public IP and only then can you use the extIP feature as it is documented on Quintum’s web site.