Would using Tor over a VPN be a good idea for crypto trading? I understand (to a point) the advantages of such a setup, but would it provide any real advantages in this case? Is it worth the extra expense?
Some exchange forbid you from using Tor, VPN or Proxy, it's likely your account will be suspended if you doing it.
In the meantime, I have installed ClamAV already, and I'm keeping as secure as I can.
ClamAV won't help you, here's a statement from their documentation.
Tip: ClamAV is not a traditional anti-virus or endpoint security suite. For a fully featured modern endpoint security suite, check out Cisco Secure Endpoint. See "related products", below, for more details.
Am I overthinking it?
Yes, your setup already more secure than most trader. I would advice you not to install unknown closed source app on your Fedora/Tails and enable 2FA on your exchange account, but i'm fairly sure you already do that.