It's too bad that the test didn't go better for you, but there are many positive things to focus on here. First, you did well on the GMATPrep CATs before the test, so you have a lot higher aptitude than your 590 indicates. It sounds like you were feeling good for the test, but you didn't perform well on Quant relative to your previous CATs, so that is obviously a place to push yourself for the retake. You completed a lot of practice problems, but perhaps in your next round of prep you could include more full CATs, and work in the
MGMAT CATs. Those should help you boost your Quant section scores.
I think retaking in 6 weeks makes sense, as you want to really improve on this score to show admissions committees that the 590 was not a good measure of your abilities. As far as study plans, I think you could gain a lot from my book
GMAT Clarity. You might quickly work through the first phase of the schedules, just making sure that you have a great grounding in all the main strategies for each problem type. Then, the final two course phases would be really helpful for you because they would help you practice effectively and take plenty of full CATs at the right time to be at your peak performance when the test rolls around.