Hi, i'm actually pretty crap at this sort of thing but I will try to help you.
using the router ip will not work, because the router is not running the software so won't know what to do with the request.
here is how i got it working, you may have a different setup, but you hopefully will know what you do/don't need to change..
Set my PC to a fixed LAN IP (WAN should be same), Setup a "service" for vnc on the router with the relevant port number if default then 5900, then setup a firewall rule on the router for the "vnc" service i just setup to my "LAN IP" of "always allow" to ensure it forwards any requests.
Then, because I am not on a fixed IP on my router I signed up to
www.DynDns.org and setup an account to give me a fixed host address, a nice short one that A. i could remember and B. would fit on the screen mine is the format XXXXXXX.XXXXXXXX.net and works fine.
Any software firewalls on the server then need the port opening also.
After resetting the router/pc and waiting 15mins for the dns stuff to sort itself out, it all then works nicely..
In the vnc bb program you go to options and set the mouse movement to 5, and set mouse to local cursor, and i find that stops any crash issues that I was orriginally having.
I hope that helps, I'm happy to try to help some more, but not sure I will be able to.