I'm sorry you find yourself in this most difficult situation. I also managed to successfully complete a graduate school program, many years ago now, only to struggle along with trying to successfully negotiate the realities of the world of work.

One of the things I know is that continually trying to fight your way along in a profession you're not suited for is a prescription for ongoing unhappiness & despair. So, while I can understand your despair, I would also like to at least suggest that perhaps, if you do get fired or resign from your current position, this can be the beginning of something new & positive. I know that's easy to say. But I'd like to believe it's true & it's what I have to offer.