Glad that your efforts have yielded some positive results - you've put in a lot of work. I wish we could wave a magic wand and cure the current driver issues, but I haven't yet found the way to the Hogwart's Express and Station 9 3/4 ....
You'd asked what antivirus I use. Because my computers are mostly mainstream models, I use Avast free antivirus & have the built-in Windows firewall on. The latest version of Avast runs a brief rootkit and system files scan the first time you turn on your computer every day, so it might not be a great choice for gamers (it might have a bit too much overhead). Like BitDefender, it rates high on the blocking, detection, and removal scores. Avast comes with the "Shields" set to a "Sensitivity" level of "Medium", which I immediately change to "High". It's a nice jump in it's detection ratings to have it set to High. And it scans everything: local I/O, Internet traffic, email, messaging, .... and has heuristic monitoring as well. Unfortunately, you also have to turn on the option to "Scan for PUPs" (the "potentially unwanted programs") - but that setting is also easy to enable. I just wish it was turned on by default. Many of the systems I clean up here in my repair work have quite a lot of the PUP type software -- some aren't horrible enough to be labeled "viruses" - but they tend to invite unwanted friends, clog a PC with ads, not help the computer in any way, and generally misbehave.
Since you've been working so hard on the recent audio/video issues, if these sessions were classes, you'd be close to receiving some sort of certificate or diploma. Your one of the experts now :)
Cheers