Hey Lokhtar,
I would say the best people to contact about the average test scores are the program directors- Dr. Leonardo, Dr. Schwartz, Dr Seigel or Bridget Lampert. They will be able to give that sort of info to you. As far as research experience, its definitely a requirement to have spent time in a lab and the more time, the better. Its really to your benefit to have a good laboratory experience base because unlike typical US PhD programs, you are immediately thrust into your dissertation project rather than having rotations or coursework the first year or so. Also, you will be asked to write a detailed proposal of your project in the first two months. So its good to have a solid background in techniques and understand time frames for completing experiments!
Definitely don't be discouraged to apply if you are worried about test scores. I think in general the program directors are more interested in what you have to offer as a scientist rather than how well you take a test :) Sometimes those two things don't go hand in hand.
Hope this helps!
Lydia