Check all the steps individually then:
- check that the ip resolves to the VPS IP at the location you're testing this
- set up the tunnel to bypass the proxy (connect it directly to jellyfin)
- check that jellyfin works directly
- check the proxy directly, with curl connected to the proxy with the header "Host" set to the domain
- check that the VPS firewall didn't block port 80
- normally you wouldn't be able to forward port 80 with a normal ssh user but I see you're logging in as root so it should be working