Help needed to improve SC from 60% accuracy to above 90%

My accuracy rate when answering OG SC is about 60% (OG 12 - Q 1 to 47 got 15 wrong; Q 48 to 94 got 21 wrong; and Q 95 to 140 got 21 wrong). I have 1 week until my exam, can experts or someone please please help me analyze what else I can do or what I can do differently?

I read MGMAT SC and SC Grail twice and made a small heap of index cards of all the key fundamentals. Now this is how i approach a SC problem:

1) I read the original sentence very quickly to grasp the meaning and to get an idea of what the "correct" one could be

2) I read horizontally all the answer choices and do the 3-2 split, group similar ones and then read vertically to decide which is better. Usually I can narrow it down to two.

3) For the ones that I do answer correctly, I catch almost 90% of all the errors why something is wrong or right.

4) I realized that i miss most in order of Parallelism, Idioms, and Tense

5) I do OG12 questions in batches of 47, 47, and 46. After each, I analyze every questions on why something is right and something is wrong leveraging this forum. For concepts I haven't fully grasp, i have an error log that tracks each concept along with the corresponding question.

Could someone please shed some light on how else I can improve quickly, especially time is of essence (I'm also week on Quant and RC) tears..........