I would boost the volunteering experience( in particular if you can get some work in the next 6 months with the most vulnerable/less fortunate populations in that will help your case) but if you can do that I think you'll be fine. You are the type of person for whom this type of plan can work. At the bare minimum, you have a number of state schools in Texas for whom you can generate interest from.
I agree with the above shadowing isnt really something worth overly concerning yourself about; spend a couple Saturdays or Sundays shadowing some local primary care doc's and that should get the job done.