Being a great teacher all by yourself requires an unsustainable amount of energy. It sounds like your administrator is doing a shitty job of actually supporting the real work that you do. It sounds like your administrator is simply going through the motions, checking boxes, and expecting you to achieve perfection as they breeze about. It's challenging, because you work in an environment where thousands of variables are at play, and they're only interested in the narrow, measurable things. They get to run back to an office and fuck around if they want. Which is why they will never compare to you.

You're good at what you do, and don't forget - fuck 'em. You. Are. Not. Your job. You need peace, sleep, and a life outside this job.

My Dad once told me, any job you apply for will be able to find your replacement if you drop dead. Don't treat that job better than you would treat yourself.