You are correct that not every school averages the score. However, the AAMC recommends treating retakes by placing an applicant's true score in between the two, something similar to averaging. Remember, the mean MCAT for MD is a 511
Since you are interested in using AAMC data, lets take a look. AAMC does not recommend applicants retake the exam because data shows that improvement is quite limited (data
here). Most retakes are +/- 2 points of the original score, which in this case is not sufficient. The OP in this case would need a *significant* improvement. At minimum a 40% increase to get to the 500 range. The data shows that about 6% of takers in the OP's score range improved their score by 10 points or higher. A 10 point score increase would be huge(!) but would still place the OP below the 50th percentile (496) and below the score that most consider to be competitive for DO programs, let alone MD.
I don't know anything about the OPs application, nor have I seen a response from them. I did not say the OP should NOT pursue a career in medicine but that the OP would be wise to consider another career path. After that MCAT score, I do think it is necessary to consider what one is up against in terms of licensure exams and the high stakes pressure they induce. If the OP decides to forge ahead with becoming a doctor, I will cheer him/her on, which is why I recommended looking into the guide for reinvention.