Hi,
First of: Sorry to read you had such a horrible experience =/
I write because I noticed you mentioned Armoury Crate and a lot of crashes.
Most of them sound like they are caused by the alt + tab issue, which Blizzard very recently labelled as a known issue: Exclusive Fullscreen Instability in Beta - PC Technical Support - Diablo IV Forums (blizzard.com)
Now, for the other countless of errors you are describing… It really does extend beyond the scope of this technical forum, but you sound like you need the insight, so I hope you do not mind 
- I certainly wished I had known >.>
I own an ASUS motherboard too, which comes “bundled” with Armoury Crate.
That tool is one of the worst things I have ever seen bundled with anything from ASUS. The official ASUS forums are filled with people complaining about the instability that “app” causes. It is bordering to root-kit with how it is installed, but you can disable it and get rid of it. You have to enter BIOS/UEFI and disable the auto-installer first, though (I know, right!?) … otherwise it will just attempt to re-installed itself after a reboot.
All that said, I just learned today that you should always stresstest a custom build PC to avoid instability issues like the ones people are describing with the beta, where hardware ends up failing. It might be of little comfort to you now, that it sounds like your hardware has run into serious issues, again that really sucks…
… but for the future:
I found a tool, which is very user friendly, that lets one test stability of your hardware. feel free to take a look if you get your PC back up and running =/
Link: https://www.ocbase.com/
Best of luck to you, and may you soon be able to re-enter the open beta!