This works but is more than is needed. Https is always a good idea. However you don't need the NAT rule. just make the webgui listen on one non default port at system>general. Then create a rule at firewall>rules, wan: Pass, protocol tcp, source any, destination wan adress, port <webguiport>, gateway default.
If you want to access your LAN clients from remote safely you should set up a VPN. There are different options. Which one is suitable for you depends mainly on your client and on the restrictions/capabilities of the remote end that you are behind.</webguiport>