I think you are right that Dway is doing something different with port 80, probably because of the Web Acceleration feature. Just to eliminate everything else, have you tried elimating the two routers and connecting directly to the DW6000?
The other thing I tried is the Shields Up! test at GRC.com. It showed every port from 0-1056 in Stealth mode.
Brad
Here are several reasons I can think of why you can't use VNC through Direcway:
1. Private IP Address. Direcway is acting like a NAT router. If you are like me your host has an IP address that begins with 10.x.x.x. These are by definition unroutable, because they are not unique.