Its not the router that is making it hard to be honest, but the DVR. See if you change the port on the DVR first, before the forward and firewall exception, it just reverts to the old port.
So first, I would suggest a Factory reset so we are back to default. No possible conflicts.
Second, set the DVR to DHCP and let it sit a couple minuets until you have a IP, then set that IP as static. Then go into the router and set a DHCP reservation for that IP.
Third, set up 3 "Application Rules" for 80,67, and 46868(Tigger and firewall being the same, type Both, and be sure to check off the check box). 46868 is in the private range so won't be used by anything else, and not one likly to be scanned by trojans and backdoors.
Next, Set up 3 port forwarding rules for 80,67 and 46868 to the x.x.x.x you have the DVR DHCP reservation set up for. (Both TCP and UDP, be sure to check the check box)
Now, go into the DVR and change port 68 to 46868. Make sure it keeps, even after a reboot. Then make sure you can access it from local 192 IP. Also, on that same local computer, go to »www.whatismyip.com/
and check your WAN IP. Then try to access that IP either straight x.x.x.x or x.x.x.x:80.
If that doesn't work, I give up.