I would not re-take unless you have a strong reason to believe you will do much better this time around(515+). Your practice scores being significantly higher than they were the first time around could be one indicator.
As is you are a competitive applicant for lower tier MD schools in the US. Really, for your outlook to change significantly and to really start considering those bigger name schools, given you already have a 508 on your record it would probably take a 516+ type effort on the retake. For the old MCAT 14% of test takers in the 27-29 and 30-32 range did 5+ better on the re-take. Not exactly favorable odds.
Your EC's are fine. Obviously given you are a CA resident there is a need to apply very broadly and thoroughly but this can be a competitive application to many lower tier MD schools across the country.