Frick,
I'm sorry to say but with your credentials, you can never get into an MSTP program. Seriously, doing what you're doing now will get you into a top MSTP program. There's no need to worry...and with your resume, a lot of programs including the UC's and Ivy's will look your way when you apply. You might want to look at the MSTP/MDPhD forum for specialized advice especially from kids like Neuronix, Habari, surge, and many other successful MSTP applicants.
Have you ever thought about staying an extra year so that you can have a more relaxed class load and focus on your research? Considering that MSTP lasts for 7-9 years, this is the time to branch out and have fun before med/grad school. Speaking for myself, I could've graduated in May but decided to stay another semester so that I can focus on my research, have a more lax schedule, and do random oddjobs in my spare time. I feel no pressure from school and having the time of my life. It's worth considering.