Just because the server itself is setup correctly does not mean you setup the network part right. How did you setup your connection to the outside world through your router/firewall and such? Can your server be reached by name or IP from the internet? http://windows.microsoft.com/en-US/windows7/allow-remote-desktop-connections-from-outside-your-home-network
Although it states for Windows 7, the basics are the same for any OS, especially the last few parts about port forwarding and getting an IP to connect to.
BTW, for 15, great description of the issue and trying to get this working, people 2-3 times your age can't explain what they want most of the time on here.