Quick calls or emails (but calls are better) to admissions offices of graduate programs that appeal to you can take away most of the mystery. "Is it a requirement for X program that I have an undergraduate degree in math?" "Roughly what percent of each year's grad students DO have such a degree?" Notice that you're asking them for facts, not opinions. By impressing them with your serious, non-desperate questions, you may be able to get a sympathetic person to engage in some speculation or advice: "Of those you've accepted without a math degree, is it your impression that a killer GRE Math score is what made the difference?" "Is there anything else you can think of that I might do to appeal to the committee?" And then, if the person is truly friendly: "I've told you my situation. What would you do if you were me?"
Remember that a graduate program (other than law or medicine) assumes that you have already established expertise and ambition in that One Special Discipline, and that you want or need the graduate training to expand and refine your command of your field. That's why those programs speak not of a "personal statement" but a "statement of purpose": In the case of mathematics, they *assume* the applicant is already a mathematician or something close to one, and want to know exactly what you plan to do during your graduate education and beyond. I mention this because in the absence of a math major and great grades, you need to prove your math bona fides in some other way. I hope a killer GRE Math score will, in the schools' opinion, do that, and wish you good luck in earning such a score.
