Before you open the remote desktop port on a router or firewall program, you will need to enable your user account to have Remote Desktop privileges on the computer you want to access.

Computers should not be connected to a router's WAN port, as this would prevent data from entering or exiting the network. Instead, a computer should be connected to a router's local area network ...

Cause from what I can see on that router it is a DSL router (DSL dedicated WAN port) with a 4 port switch and a wireless AP in it. It can't talk to a cable modem as a router.