I’ve literally been on the same issue as well for the last 2 weeks. I wanted to setup P2P multiplayer with the collab viewer template over WAN rather than a local LAN network but can’t get it running. The problem I have found is the port only works locally and, despite forwarding it, my server specification will not work with the public IP, only the local/private IP. Unreal documentation recommends NAT traversals ontop of what you’ve done in your screenshots - all of which combined are just too much and too complicated.
The solution I’ve found is a halfway house. I’ve ended up using ‘LogMeIn Hamachi’ to link two computers into a same low-latency and low data transfer server then connected through there. This works just about for my purposes.
However, my suggestion would just be to say screw it and go for the full dedicated server hosting of which I’m sure you’ve seen many tutorials and posts advertised for - like AWS or SteamSubsystems etc