Regarding DX4000 security and static IPs

That is wrong, that is your issue
By default, when File and Print Sharing is enabled it binds to everything, including TCP/IP (The Internet Protocol), rather than just the local network, meaning your shared resources are available over the entire Internet for reading and deletion, unless configured properly. Any machine with NetBIOS enabled and not configured properly should be considered at risk. The best protection is to turn off File and Print Sharing, or block ports 135-139 completely. If you must enable it, use the following guidelines:

so at the risk of sounding like a moron (though i’m probably already there) shall I delete that rule from the router config?

what was the lan ip address. I mean you do not have to tell me but is that your DX?

is there a way I can I direct message you or otherwise some form of private communication?

look at your avatar top right and you should see a msg from me