Do schools look down on the essay if you use significantly less than the minimum characters allowed? Mine is at 1750 out of 4500. I can make it longer but I really like it as it is now.
This could be tastefully done. I would advise against it unless you would color yourself an advanced writer. If it's average writing, it might turn away some. This is just my opinion though.
A little short is fine. Less than half the length seems too short. We can't see your essay though. If it's short but brilliant, it's fine I expect. If it's average and short then being so short probably makes it below average. None of us quite now though since we're all in the same boat you're in. Good luck!
You don't need to be right at 4500, but 1750 is too short IMO. That's only like 300 words, and I just wonder if you can really answer the question properly in what is basically two paragraphs at best. Probably about twice that, in the neighborhood of 3500 characters, would be better, unless your 1750 words is truly mind-blowing.
Using exactly all 4500 is not necessary, but as others have said, 1750 would stand out for it's shortness. You haven't even used half of the max. But if you love it the way it is, I would worry that by trying to make it longer, you would just be adding meaningless "fluff." I would have some people proof read it and see if they think it is adequate.