Couple of Questions (restoring backup, reverse proxy)

[TheDreadPirate]

Your Cloudflare domain should be pointing to your public IP. Which you cannot get from docker. That 172 address is the local IP of the container.

You'd need to look at your router's UI or use a site like "what is my IP" to find your public IP. You should also consider using this docker container to dynamically update your Cloudflare domain if your public IP changes.

https://github.com/favonia/cloudflare-ddns

To use NPM with Jellyfin, you would need to publish ports 80 and 443. Which you already did. What does your Nginx config look like for Jellyfin? Are you using the Jellyfin's bridge IP? Which WOULD be 172.X.X.X. You do NOT need to publish port 8096 in the jellyfin docker config if all access to Jellyfin will go through NPM.