My question for you is: how is that your strongest piece, given your teacher clearly does NOT think it is? (assuming you have above an 83 in the class?).
I don’t think an 83 is a total dealbreaker, but I would definitely want to explore the reasons why you think it’s so strong if your teacher doesn’t.
Do you have other essays with a better grade?
Why do you like this one so much more? Maybe it’s the right essay to send, but I think you’d need to answer these questions for yourself first.
I personally feel like if you have a solid A in the class and you are a very good writer (as evidenced in your essays), maybe submitting a quirky, interesting essay that really speaks to who you are as a candidate is a bold move, even with the 83? But it would have to be for a very mindful, deliberate reason, IMO.
As for other schools who do not require an essay: I would NOT send any extra items they didn’t ask for. (especially one with a meh grade).