Aw Blackroses, sorry you had a disappointing test sitting.

Not time to quit, though, if you're serious about attending a place like Mudd.
I second what Battlo said. Bummer that you were taking your subjects for the first time in November when planning to apply ED, but it ain't over till it's over. If you were my son applying last year, I'd advise you to still apply ED if you're certain that Mudd is the right place for you, and make the case clearly as to
why it's the right place for you -- fit seems to be very important to HMC. If the rest of your "package" is solid and test scores really are the thing that would break you, then you may get deferred to the RD pool, in which case higher retake scores will help you.
You might not have tested as poorly as you think -- remember, the scores are normalized. But let's assume you did. Why? Were you sick? Did you just have a bad test day? Or did the tests cover material you haven't worked with before? If the latter, then you have some prep work to do between now and the December test sitting. Get some SparkNotes, a test prep book, whatever is available to you, and teach yourself that missing material. My son had to do this for his second subject test; his high school coursework didn't cover everything that was on the test. If that's where you find yourself now, know that it can be done, but it does take a significant investment of time and effort.
Good luck!