Everyone I have talked to has told me that GPA and MCAT score is what really matters.
Surveys of medical schools admissions by Kaplan over the past several years where about 2/3's of all MD schools responded consistently show MCAT and GPA are cosnidered the top two factors by 75% of the schools. AAMC acceptance data more that supports this.
I have a 3.8 and I am concerned because there are only about 30 D.O. programs in the U.S.
I agree with doc gray on this is why are you only looking at DO? From the limited data I have, I estimate about 50-100 people over 40 start MD school each year in the US. I can certainly list specific examples
I still have physics and organic chemistry left but the MCAT scares me to death. I took microbiology over because I got a B.
Rule 6: The MCAT is your friend
Rule 10: Beware of FUD -- Fear Uncertainty and Doubt
The MCAT is the most effective and efficient way for an older student to improve chances in medical school. Repeating a course that you got a B, while I can see why you felt you could do that for DO school, I would suggest that you would have been better served by using the time, effort and money to prep for MCAT. Dont let the premed neurosis take you down paths that are just not going to be that helpful in the end.