Acro Yali,
I don't know about the percentage needed for passing. It has been rumored for years to be 55-65% by many, but I have never seen it from any NBME sources or publications.
In reference to your question, the NBME CD (released items) seemed to be very similar in style to the exam, however believe it when everyone says that its easier. It was much shorter, simpler than the exam. Good luck.