I suggest doing Americorps for a gap year to leverage your advocacy. You could continue in your nonprofit. You are a stronger candidate for MPH only right now, and you should think about this.
The DUI hurts your chances, especially if this was a year ago.
You must set aside more time in a clinical setting, especially with scribing or shadowing.
You may have to retake the MCAT to give yourself enough time to allay any concerns with the DUI (meaning a couple more years from now). I'll let the other experts chime in.