how should I "read" the passage?

Hi everyone! so i’ve gone through about 20 SATs (critical reading sections only) this summer in the hope of increasing my score from 600 to mid 700s. I didn’t notice any improvement after so many tests and decided to untime myself. I then got in the 700-720 range with 15 extra mins. and that’s all I got out of the 20 tests, and it was inexplicably frustrating.

However, I developed a strong sense of looking for the “correct” answer. I could now identify my obstacles as:
-poor comprehension (I have trouble understanding and I have to read several times, and I also do not sufficiently assimilate the content.)
-lack of nimbleness in relating ideas in the passage.
-vocabulary
-sentence completions - “logic”

What should I do to resolve these problems, and how should I “read” the passage? Noitaraperp’s method can’t help by the way, since my problem does not lie in understanding the questions, but in understanding the passage.

Thanks in advance!

quick edit: I got essential 500 vocabs and erica’s “the critical reader” book.