Only 600 (Q32, V39) - how to improve quant?

I wrote the GMAT this afternoon for the first time, and though I didn't feel completely ready, I didn't anticipate scoring so low on the quant. My intial GMATprep score was terrible - Q34 and V24 (total 500), though I was admittedly not paying much attention and was extremely tired. I also took the verbal section on that very lightly because I am a little overconfident in my verbal abilities. I didn't expect that I would actually go DOWN in quant...because I felt like I knew NOTHING about quant when I wrote that GMATprep about a month ago.

I have always been decent with English, logic, grammar, and those kinds of things that appear on the verbal section, though from a few quick google searches it seems that this score breakup is very uncommon. I finished the quant section with 20 minutes left (got nervous and rushed through it), and I knew that I had done badly because the last question was ridiculously easy.

I have gone through all the Manhattan books and did many of the questions from the OG Quantitative review, and had particular difficulty with number properties, algebra, and DS questions in general. Can anyone suggest how to remedy my crappy quant score? Will going through the OG really be that beneficial at this point, if I've gone through all Manhattan books + OGquant? Or should I look into doing a course? I'm shooting for a 650 score so if I can get quant up to Q40 while maintaining my verbal, I should be fine. Which is a little embarrasing, as I see that Q40 corresponds to 56th percentile - I thought that I'd surely be able to achieve that.

Also, a bit of a general question, can someone also explain why so many people are scoring so high in quant (I feel like every thread I read has Q49) and then some much lower verbal? I feel like most people would be better at verbal than math but it seems like that's not the case.

Any help is appreciated.

EDIT: sorry if this is in the wrong section...please move if necessary.