I just took the Jan. 21st SAT, and even after a (useless) $7000 prep program 2 hours away, my final score was 1390/1600. I got a 1450/1520 on the PSAT, so I had high hopes.
R&W - 690
Math - 700
Essay - 8/8/8
Normally I do worse on math. Idk what happened…
Which books should I get to improve my score? I got the Erica Meltzer Reading (not Grammar) and although it helped, I’m still missing 7+ reading questions each practice test I take. I’m good with writing, but math is also somewhat hard for me. (I know, dumb)
Please help, my parents are weeks away from disowning me.
I hope someone will help us both 
Use the free seven collegeboard tests! Those are the most helpful tests since they come straight from the makers themselves. Since I also need help in reading, I will give some math tips: practice as much as you can until you understand the topics. You must be making dumb mistakes (math error or misread question etc). Always figure out how to do the incorrect question (first try it yourself before seeing the answer explanations). If you have time, try memorizing math hacks for the noncalculator part (fractions to decimals, Pythagorean triplets etc). For calculator, this section is a bit trickier but honestly as you practice doing the questions and understand (you must understand) what went wrong, you will definitely improve. If you’re too confused on what went wrong, search it online, ask someone for their perspective, or just ask on college confidential.
I really liked Princeton review book since it had lots of reading/writing tests to practice with. Other than that, I also am a bit stuck how to improve reading (well just a little more practice…)
Good luck!