We tried fixing that via private messages, but I've got no clue what kind of router he has and the screenshots are very strange with labels for ANY -> 3306.
Maybe you've seen that kind of router before and might be able to help.
I won't paste the screenshot link myself here, but maybe you want to share that with Rob as well and see if he is able to help you better?
I fear like this is out of my reach without hands-on support as I myself haven't had a public IPv4 address for 5 years now.
(German ISPs even turned off the dynamic IP stuff and went full-on DS-Lite/Carrier-Grade-NAT on IPv4, but at least we get a decent /48 IPv6 network that should have enough addresses for all devices and atoms in my house