I'm screwed when it comes to the Critical reading portion of the SAT (Really need some help)

I’ve done all of the Critical reading practice tests in the SAT study guide. My scores hovered around 540-600. Horrible scores i know. I’m aiming for at least a solid 650 and at most a 720, but it seems that i won’t achieve that goal. I’m pretty good at the sentence completion, but i have problems with the passage-based questions. I underline and circle key words, and skip questions that give me a hard time but i still fail.
.I also found some SAT practice tests floating online. I took those and got 570s on both of them. After completing an entire practice test under timed conditions, i usually go back and try to fix my mistakes and thoroughly pinpoint where i went wrong. The only problem with this is that the SAT study guide only provides the answers to the questions; not the reasoning behind the answer. There are even some questions where i have no clue why the answer is the answer, so i just remained stumped even though i’d spend a good chunk of time trying to get to the correct answer. I’m taking the SAT in less than 2 months, and frankly, i feel that i’m screwed. Am i doomed to crappy critical reading scores or is there hope? I really need some help here.

This is hard to explain, but once you can pick out which questions on the test are the easy ranked questions, and which are the hard ranked questions, you can easily figure out that 90% of the time, the hard ranked questions are not going to be the obvious/blatant choice.

Guess its too late already, but if you have the blue book, the explanations to the answers are here https://account.collegeboard.org/login/login?idp=ECL&appId=0&DURL=https%3A%2F%2Fsatonlinecourse.collegeboard.com%2FSR%2Fhome%2FbookOwnerArea.do%3FfromSecondEdition%3Dyes