I wouldnt say the audio is horrendous at all.
Audio levels seem fine from what i listened to.
I know you had some enhancements activated but mess around with a few things and you should be able to fine tune it to take care of your breaths/background noise.
I personally just use nvidia broadcaster and it cuts out fan noise entirely and keyboard because I just have a cheap setup.(Might be resource intensive depending on your setup)
As far as manually cutting out breath and mouth sounds that can be fixed via adjusting your noise gate. I Actually run my audio through a program called audacity mainly to get rid of breathing in the whole audio track with just a few clicks.
Im 50 videos deep and your setup sounds better than mine so dont be so hard on yourself 👍