Just to clarify, you mention a 1 year masters program but then list a postbac GPA. Which one is it or is it both? Typically graduate (masters) programs have graduate level courses that are listed on a separate line and not included in your undergraduate cGPA and sGPA calculations. A postbac however would involved additional undergraduate level courses that would not result in earning a masters degree. What you describe sounds like a graduate program.
As for what to do: if you can volunteer in clinical or nonclinical settings that would definitely be a good thing to do during this time of need. Shadowing is always good but you need to target primary care - surgery and cardiology are fine experiences to have but you need primary care in the mix. Taking a lab position is fine as well. Research experience is helpful.
Really, anything you do will likely be just fine. Minus your GPA and lack of MCAT, your numbers are pretty good.
