404 is the code for File Not Found Error.
In about 99.9% of the time, this is caused by typos or outright entering completely bogus information. (i.e. I've seen people try and enter the PLS link of Shoutcast or the address of their homepage in there)
For help with that, tell us the URL to your shoutcast/icecast server (i.e. 18.104.22.168:8000 or example.com:8001 etc.) and what your current Statistics Relay loks like.
For the requests and website system, port 3306 will serve you no purpose if you're running Firebird.
Theoretically you can connect to Firebird from the network, but you need to secure it yourself and you need a webhost that has the Firebird module for PHP installed. For the security, I can't help with that other than pointing you to the manual: https://firebirdsql.org/en/firebird-rdbms/
Hosts with Firebird/Interbase drivers installed are super rare, but you can probably find a few smaller ones where you can install/enable your own extensions.
Firebird is rarely, if ever used on the web, though and there's little to no help you can expect from either this community or the internet in general when it comes to setting that up with SAM.
You're way better of if you just switch to MySQL/MariaDB. (HeidiSQL is just a management tool, that is completely unneccessary to install for most people)