I'm not familiar with Avast, so I can't comment on its performance, but I'd suggest that maybe you've been stuck at arrivals for three days is because you're at the highest state of security threat and you've effectively locked down the airport. I agree that it not straightforward and it needs tweaking. To be fair as with all this sort of stuff it's about risk. If you get loads of emails from friends who forward all sorts of stuff they get with links etc and you download lots of free software etc. then your risk of getting a virus is much greater than those who just have a few commercial programmes on their machines and work in a more business like manor.
I would strongly suggest using Microsoft System restore so that you can roll back your PC to a previous state, that solves a lot of issues for home users. Also backing up your documents and valuable data. I'd suggest an online solution. One good option would be to move all of your data into the cloud and store everything in dropbox or similar, this has the advantage of syncing your machine onto more than one device and they worry about the backup for you.
We also use a pre filter on all of our email, so we don't scan any email on machines as it is all done before the mail even hits our mail server, we bin around 70% of the email that is sent to us (company wide) so it shows how much unsolicited email is out there. I'm sure a lot of email host will offer spam and virus filtering.
I'd also suggest using something like CC cleaner (free) to give your PC a clean up, this will pick up malware as well.