I was sorta in your position too. I've been accepted, and I'm sure my ECs are nothing compared to yours (working, TAing, tutoring, ER volunteer..). Don't take my word for gospel, as I have also been concerned about mine, but I don't think it's the hours you put in, just that you were committed to something you want to do. So a few points:
Shadowing the physician is good. If you think you've seen everything from them, try to shadow another specialty (I especially enjoyed Orthopedic surgery)
hospice is good, as I've seen goro say that the hospice really shows you want to work with sick people
autism and mentoring volunteer, you're fulfilling a need in your community for the long term
Research need not be medically related (know someone who got interviews and did research in psychology lab), and not all schools require it (it helps though). I didn't have much research
Pretty much, as far as the other competitive students, you're not competing with them, you're competing with yourself. It's not a numbers game, just "would you make a good physician, and spend your working life with sick people". If you can put in 3-4 hours a week in a hospital ER or something, I would recommend that. Everyone's done that, and my interviewer asked me about mine.