Uhhh, probably not a good move if that's true. US News Rankings are based primarily on research - that's why nobody is ever going to beat HMS with their four pre-eminent academic medical centers. MCAT is weighted 13% in the research rankings and only about 10% in the primary care rankings (
http://www.usnews.com/education/best-graduate-schools/articles/medical-schools-methodology).
Why are you citing an almost two-decade-old study when a newer one is clearly available and shows data to the contrary? That is, there is no statistical difference between HuMed students and their traditional peers in USMLE Step 1 failure rate. I cited the newer study above.
No, you're ignoring the fact that there are likely many confounding variables with students who have verbal SAT <= 650. In order to show that A has predictive power over B, there has to be a graded dose-response relationship. This is why dose-response curves are so important in medicinal chemistry. It means nothing if your drug works at 60 mg dose but then drops off completely at everything below that. That just means that your drug isn't very predictable and pharmaceutical executives understandably don't like that. They would say that there's no dose-response relationship here on the SAT. 650 is a high score on the SAT. In fact, it's the 89th percentile. Does that surprise you?
It surprises me. Basically, they're saying that there's no relationship between candidates' SAT scores and USMLE Step 1 score but everybody who failed the Step 1 was below the 89th percentile on the SAT. In a group of 100 people, that covers 88 people of the group. That's like saying, "Everybody who was rejected from med school A was a U.S. citizen." Well, that's a bit obvious since that includes most people who applied to that school in the first place and stacks the deck in your favor. This only emphasizes the point that the SAT is a very poor predictor of Step 1 performance.
Also, for the reason I mentioned above, med schools probably aren't as concerned about MCAT average as you think (except maybe mid- to low-tier schools). MCAT score is weighted only ~10% in the USNews ranking. Research-related factors account for the lion's share. That means that schools get a lot more bang for their buck in focusing on getting more NIH funding than raising the average MCAT score of its students.
That would be interesting and I believe there is no data on this except in specific specialties (OB/GYN comes to mind). It's hard to measure and I suspect there is no effect at all.