Graveyface, I realize that your primary purpose is experinemting with VPNs. If I understood your first post correctly, the task you were trying was to provide service limited to a single server. Normally, we would use the following approach for that:
How to Port Forward Service Ports (Webservers, RDP, OWA etc..)
Having said that, I would try defining 'Internet' in your above question as:
Name: Internet
Address: 0.0.0.0
Netmask: 0
Interface: [whatever your external interface is]
Anyway, thanks for the interesting questions and the clear explanations of your situation.
Cheers - Bob