I tried portforward.com, but I got stuck at the IP Address part. Are you sure this site is for Mac? It looks like it only will work for PC...
And sorry, but what is the VPN settings? (Sorry for my lack of mac knowledge. Again, I'm new to mac.)
Go and find your physical router... In your house... Find out what make and model number it is... If it is an Airport router, you can follow this guide, if it is other (and airport) you can use
www.portforward.com Although done on a Windows computer (not a fecking PC - PC = Personal Computer not Windows computer), the process is almost identical on a mac... You chose your favourite web browser and type in the IP of your router.
Tell me what model and make your router is.
VPN - Generally is a Virtual Private Network. Programmes like hamachi are these, they pretend a cpnnection over WAN is a LAN connection(very roughly explained), I dont see why you would need to use this in this instance.