You cite interviews naming the person interviewed and the date, with the term "personal interview."
Citing yourself has no value, as your qualifications are established as the author. The purpose of citations is to bring additional people to the support of your position, thereby to strengthen your position.
You have no basis for legal action, as your paper was graded correctly.
I have taught college classes for over twenty years. During that time, I have awarded some low grades when the student earned it.
I have NEVER heard of any student suing (much less successfully suing) a college or professor over a grade.
A significant challenge would be proving that your judgment on grades is equal or superior to the professor's. Another obstacle would be in proving the economic loss you suffer because of the grade on your essay.
Use the lawyer referral service in your community or the one at www.calbar.gov. The initial consultation with your attorney will help you see what option are available to you.