Quant usually maxes out at 51 (99th percentile). There isn't a set number of questions you need to get right - the score is based on the difficulty levels of the questions and the specific mix in which you get them right / wrong. (eg, if you get the last few in a row wrong, you won't hit 99th percentile.)
To hit the 99th percentile in quant, you probably need to get 80+ percent of the questions right (though we don't know for sure, as that info is not published by the people who make the test).
You mentioned having a lot of time left over on the verbal even after double-checking answers. If you have 10 minutes left over, you're still moving too quickly, even if you did have time to double-check everything. You're not double-checking thoroughly enough or working systematically enough or
something - if you have 10m left and you aren't getting the score you want.
When you study, how much time do you spend analyzing problems after you've already tried to do them? Generally speaking, that's where most of your learning occurs - in the analysis afterwards. If you're not spending at least twice as much time analyzing, then you're not spending enough time really learning what's going on.
Here's an article that can help with that:
http://www.beatthegmat.com/a/2009/10/09/how-to-analyze-a-practice-problemSo, you need to do more work on verbal, yes, but you also need to do some work on quant. If you can lift your quant to, say, the 90th percentile, that takes some of the pressure off of the verbal (though, obviously, you still do need significant improvement on the verbal).