Hello,
Disclaimer: I have no personal experience with the schools you mention.
If those three schools accept the MCAT in place of the GRE (which they all appear to do), by all means, submit that. If you have taken any statistics courses, computer science courses, or other science classes that required you to demonstrate some quantitative ability, you should be fine. As a biology major, I don't think they'd hassle you too much; my guess is that schools tend to pay more attention to indicators of quantitative ability for students with social science or humanities backgrounds. On the other hand, if you're an excellent test-taker with $200 and several hours to blow, you could probably get a strong GRE score to bolster your app.
The Kaplan teaching probably won't count for much. The 4 years of research and the publications, on the other hand, are great. Play these up in your application, particularly if they are in an area that is related to what you want to do in the future. But make sure you also spend time explaining what you plan to do with your MPH studies/degree and how the MPH will help you reach your professional goals. The sense of maturity and purpose you convey will help you more than the specifics of your previous experience.
I think people who apply to MPH programs as a backup for or a stepping stone to med school tend to be frowned upon, but since you really intended to get an MPH, this should be less of a problem for you. It's OK to say you also plan to get an MD, as long as you tie everything in to your public health interests and make it seem like it's all part of your plan.
My guess would be that you have a decent shot at any of these three schools.
