Problem Solving

I need help understanding something about the Official Guide. I am taking the test in 6 weeks, have been studying for 2 months, and first got a 450 practice without having looked at math or having taken a test for about 12 years. My lowest scores are the problem solving and data sufficiency. I need a 600 to get into my school of choice. I am trying to figure out what the level cut offs for the problems are. For example, I am up to question 109 in problem solving I am wondering how to figure out where the 700 level questions start etc. I really want to try to focus on building my skills for being able to achieve over a 600 rather than taking on math that will be way above my learning capacity for the time I have left. I am still spending a generous amount of time on each problem trying to understand the math. This makes it clear to me that it would be best to improve current skills and know how far I need to go to reach my goal. I also want clarify something about the data sufficiency. It seems that if you have a certain level of problem solving/math skills, doing many practice questions is the most helpful tool. (as opposed to having to learn/relearn concepts) I guess the question here is-are the math skills, coupled with tons of practice problems sufficient for DS?