Dont worry about the files that cant be scanned, they are password protected or the system cannot find the path etc…
If you want to buy something you could use Malwarebytes PRO which costs 24.99 dollars for 1 PC LIFETIME LICENSE.
Or you could use Comodo Firewall, which is more an Firewall but it also scans for viruses, BUT THIS COULD GIVE PROBLEMS WITH AVAST.
So i would consider Malwarebytes, also you can get rid of Adware and PUPs with it and its blocking Websites. 