Hi, I also have a similar plan but I am undergraduate that studied Applied Math and Computer science.My experience will be alot different from yours. I find that if you had a degree in Math or curriculum that was surrounded around discrete math you will have a very good time improving your scores.A physics curriculum is also beneficial. My ability to improve and notice my mistakes are much greater however, I still make careless mistakes from time to time(Because I dont read the question carefully or rush through them). I wind up scoring a 161 on diagnostic with 10 minutes to spare(A mistake on my part). In only 4 weeks of practice my score skyrocketed to 165(With 10 minutes to spare and is still a mistake considering that I can spare 5 minutes checking answer) and I will continue to use the same strategies to score a perfect quant.I also didn't constraint my practice what do I mean? Meaning during practice I give myself unlimited time to think and check my answers.If you are making arithmetic errors slow down and triple check your answers. This is easier said then done since during my classes computational errors are absolute bane of existence. This means using more scrap paper and showing more work. Once you are making no errors on those,slowly decrease the time and avoid using calculator unless absolutely necessary. Some tools I study with are
Magoosh math,Manhattan 5 lb math problems,Nova, and Official GRE math guide.