Until you're scoring 48+, you don't need the difficult math problems. My advice is to get the OG and start working the problems. You may have already done this, but you should do it again. Truly analyze every quant problem in the book. Don't take the OG explanation as the best explanation - try to find alternate ways to solve every problem. Find some sort of rule or takeaway for every problem.

This takes a lot of time and a lot of work... some problems might take you half an hour to really dig into... but this is the best way to improve on quant.

Thanks for your response. I will work these and look for something from every problem. Should I even do this for the problems I answer correctly?

Definitely! Sometimes you may get a problem right out of sheer luck, or maybe you got it right but not in the most efficient way. Analysis is always a good idea.