Typically, Linux doesn't need antivirus software like Windows do. The attack vectors are different and the frequency is significantly smaller. Also, there is no (consumer-grade) robust antivirus software for Linux compared to Windows. Like you mention ClamAV is only useful for a very specific use-case, not a general purpose one.
I think enabling firewall is good thing. Personally, I am not that security conscious but we have many users that do. They may gives you better advice, but the again take everything you read on internet with a grain of salt. Don't make yourself too paranoid about everything. Be safe and cheers!
