You need a plan to attack SC. I'd recommend mastering the concepts for SC before attempting any more practice tests. As you can see, practice does not make perfect. But practice with mentoring and guidance can make all the difference.
Some concepts are simple, others are more complex. If you master both, you can ace each question with confidence. Here's a free lesson
on SC strategy here, you can learn more inside the SC Pill
. I'd also recommend checking out the practice pill database of questions, you can practice on more CR there and get the expert coaching you need to score 700+.
But really, focus more on how you think and less on the number of practice questions. Try that new strategy going into your GMAT exam and you should start seeing some scores that do not resemble the scores you got in the past.
... and more
What's Inside GMAT Pill?
Zeke Lee, GMAT Pill Study Method (Study Less. Score More.)
GMAT Pill Reviews | GMAT PILL Free Practice Test