I think I need to start with some easier questions.
Is it normal for the Apollo BTC to run its fan at full speed after shutting down?
Any way to fix that? Or what am I doing wrong?
I have no idea what you're doing here and it seems you aren't either.
IF the miner is connected to the internet and mining, you are online. My educated guess is that you fucked up your VPN config. It's also highly likely that your pool info isn't valid. That's why the miner isn't working in your other tries.
Do us a favor and
0) Reflash with the factory image
1) actually read the manual
2) connect to the Apollo via ethernet
3) configure the mining pool settings
4) wait for the miner to start mining
5) OPTIONAL: Start tinkering with the device once everything works.
6) Check if the node sync works