SAT Math score won't change?

Hello! I’ve been practicing for the January 21st SAT, which would be my first one. I’m a high school junior and I want my score to be around a 1400/1500 by this November for early decision applications (I want to apply to WashU ED). My reading score has improved a lot since the first practice test(w/o prepping), but my math score has stayed about the same.

Total Math R&W
1090 560 530
1180 560 620
1210 570 640
1180 550 630

I’ve been using Khan Academy along with other free resources, but it hasn’t really improved my scores that much. but I’m also not very good at prepping everyday. I’ve been considering taking the ACT instead, since the math section has less weight, but the time limits are what turned me to register for the SAT.
Basically, what other free/affordable tools or techniques should i use to improve my math score? Recommendations for the reading/writing section are welcome as well as I need to improve that score too.