The scratch work nonsense and accusations of your answers being similar to others in the classroom are standard excuses ETS makes to arbitrarily cancel the scores of ethnic minorities, mainly those of Asian origin, but unsurprisingly, I guess they are targeting African-American and Mexican students as well.
Under no circumstances will you win any type of appeal, even if you decide to take legal action.
You can send teacher recommendations extolling your exemplary behavior, transcripts that showcase a perfect GPA, receipts that prove you took an expensive 8-week preparatory course and scored similarly each time, lengthy explanations as to why you did badly on the PSAT or why your scratch work shows inconsistencies, etc.
Your only option, sadly, is to heed the advice of others here and opt for a re-test. The good thing, however, is that you can score up to a 100 points less on the retest than your recent score, and your original score will hold.
Great luck!