I have been trying to set port 443 so that I can access my NAS from the internet. I have set the port with a private IP and DDNS which allows me to access the router from the DDNS name on the LAN but not WAN. Any help would be welcome.

Is the vigor remote management already configured to use 443? If so put it on something else... such as 8443 and then your rules should kick in.

The remote managment is enabled but can't see how to check what port it is configured to. Could you advise?

System Maintenance >> Management -> Management port setup

You don't mention which version of the firmware you are using. I use port forwarding for my NAS box and a wireless access point. The port forwarding to the NAS box stopped working with the last firmware but not to the AP! However with the latest firmware it is now working again!