It’s hard to conlcude from what you wrote, but to me it looks you’re jumping from trying to run sys-audio to trying to run other qubes whose audivm is sys-audio. Do not do anything else until you are sure you can hear sound from within sys-audio, meaning, until you have fully working sys-audio. You posted two links, and there are other settings in that guide regarding sys-audio.
Also, I’d try creating sys-audio using this guide, if the one you tried didn’t go well. Then come back and tell us exactly what you did, so you could be easier to be helped.