You might want to use another antivirus if it throws too much false positives on you (that is a common tactic, otherwise how would they lure you into regular subscription?)
Nowadays you will be fine with firewall (router or software solution like Comodo) and just Windows Defender (or Security Essentials on Win7).
As additional measure, if you download any executable\archive from internet, check those with Virustotal. If you see 1-3 results out 70 - it’s more likely false positive (especially if there is a generic\heur words in names).
With Pyfa 2.0.2 as you can see with check results, out of 53 available engines not a single one detected any threats (including Symantec engine):
Ofc it’s your choice in the end, but I’d uninstall Norton to save system resources, and subscription money can be spent on something more useful (like backup storage or something).