if you are finishing 50 question q-bank blocks in 35, tiime shouldn't be an issue on the real deal. i don't know of anyone that had problems with time, other than the fact that 8 hours of exam in one day is just a lot of work. but, i had plenty of time on all the blocks.
i think that for the last 3-4 weeks it is highest yeild to use q-bank to direct your studies. do the 50 question blocks, and read all the answers. learn the details surrounding the questions that you missed, know them cold. also, use first-aid to direct your studies.
if i could do it over, i would hit the stuff i missed, and the stuff i didn't like a bit harder. i also wouldn't even spend any time learning stuff that is not in first aid or tested in q-bank. think i paid too much attention to the stuff i sorta knew...very bad idea. the test covers a huge range of topics, but i think you have to really just know a lot of basic info very, very well. and almost every test question had a similar q-bank question and/or was in first aid. know all that cold before you start reading robbins cover to cover...
i started with average around 55% also, finished with an overall 60%, but more like 65% for the last two weeks. i even had a couple 90% blocks. also, i reccomend the NBME self assesment tests. they are very much like the real thing, and give you a decent idea about where you are.
as for correlation, i think that if you are over 70% q-bank the last week, you will beat the mean. if you are over 60% toward the end, you should pass. that area between 60-70% could be anything. i was doing 65%, and just at the mean on the nbme, and i was surprised and disappointed to get a 192/78 on the real test.
anyhow, best of luck. do you work, and the test is actually very passable. i was surprised that it didn't seem as hard as i thought. but, i think that to get a great score, you have to really do some serious prep work. and there is a lot of luck involved, whether you get a test that hits your strong or weak areas, whether you guess right on a lot of the 50/50 questions, etc. but, if you do your work, you WILL pass it.
hope this helps, knock em dead! the test deserves your respect, but not your fear....