Re: I think I'm feeling burnout or worse. I am seriously considering walking away.
Leave this dojo. Find another one. Don't let anybody tell you that it's because "you don't have what it takes". That's how abuse is justified. And there's a fine line between "hard training" and "abuse".
Training should be challenging, but should not feel like punishment.
Seriously, look for another dojo. Nobody says leaving your current one has to be the end of your aikido career.