How can I improve my quant score? Any resource in particular?

Hi all,
Firstly I would like to thank this community for the amazing posts and discussions that have really helped me through my GMAT journey so far. I'm still struggling with my prep though so thought I would reach out with my story and hope for some advice!

So I started my prep at the beginning of october this year. I signed up for e-gmat's verbal and quant course. While I was completing verbal I read about TTP's great quant course, and decided that I would go with that for quant. The explanations and course work were great but it takes really long to go through all the practice tests, and about 70% into my course I looked at some OG questions and found myself not being able to solve them, despite having performed decently in TTP's practice tests. So after completing that course I also bought the MGMAT complete guide and went through that. I supported that with some questions from scholoranium and also GMAT club tests, but inspite of all these resources I just was not able to get to more than 55-70% accuracy in quant. I gave my exam last week (in the hopes of submitting applications in time for round 2) and scored a dismal 620 (Q38 V37).

I know I have not had enough time, but despite using all these highly rated sources I have just not been able to get up the mark for quant. I'm aiming for top b-schools and need an overall score of about 720-740, and for this I need a significant improvement in quant. I've found that I understand the concepts when I'm learning them, but few days later trying to apply them becomes a problem, and also trying to solve them in a decent timeframe. I gave a Sigma Mock tests a couple of weeks before my actual exam and scored a 650 (Q39 V40), and scored a 44 in one of the quant CAT's I have on GMAT Club tests. Some practice tests I've also scored much higher (70-80%) over a breadth of topics so it's not like there's one in particular I'm struggling with.

Basically I'm just not sure what's wrong, and how I should work on quant from here on out. Should I try new material? (heard Math Revolution is really good). Or should I keep doing what I have been and just practice more? I have to retake the exam before 20th Jan, so any advice that the community can offer would be seriously appreciated.

Thank you!
H