You have to use the advanced console to add rules to get RD on non standard ports. Note the MSTSC is the client (the C) and not the host. Open windows "firewall with advanced security", do to inbound ...

In Part 1 of this tutorial series, we configured Windows to accept remote desktop connections, so we can log into and use a PC anywhere in the World with Microsoft’s Remote Desktop Connection client ...

I don't think you can remap the external port to a different internal port on the linksys. I think your only options are to change the port in the registry or buy another router that supports ...