To be honest, I'm not even sure we still need Anti-Virus in 2016. I haven't had a virus in years.
Depends on what kind of user, surfer and downloader one is.
As for me, no need for resident antivirus, nor whatever third-party firewall.
At the very least, I would recommend using an anti-exploit. Also, have your PC and browser properly configured, with a few good extensions. Lastly, I suggest to use a few passive defenses which use little to no memory (hostfile(s) + browser "vaccination" + resident ad blocker at OS level, not at browser level).
Doing P2P stuff would require other, additional protection.
Oh, I was about to forget: happily surfing as Admin on XP.
Modern OS are pretty secure.
Out-of-the-box, I seriously doubt it. Fortunately, they can be hardened afterwards, at little to no cost.
Yeah. I'm not sure people would trust such a disclaimer. I'd believe the opposite of whatever was written.
With computers, one only has to know and understand what he is doing / what is happening.
It only requires having a bit of common sense, as well as being logical. Reading a little helps, too. Nothing big, really...