I have never felt like such a failure. I hardly sleep. I have no time to think before I’m bombarded with another litany of demands and questions over why something hasn’t been finished.
I have over 5 years of experience and it has never been this stressful and demeaning.
You're not a failure. You've been failed by the company.
The story you've told is that they are totally unreasonable. I'd accept that this position is a failure. Get a good night sleep—you can't fix it.
What to do? Well, I'd probably tell people to "back off," see if I(you) can help, and if not cruise through a paycheck or two before leaving. Depends on your situation of course.