I would suggest using NextStep and Kahn Academy for CARS. These are the only resources I used and I was able to increase by score from a 122 on my first MCAT to a 127 on my second. I didn't really start CARS specific prep until about 2 weeks before my exam, but doing practice questions for all sections definitely helped as general practice will help increase your reading speed/ability to find key points. Timing is also HUGE, and if you are missing that many, you clearly need to work on your timing. This is not something that you can improve on overnight.
If you have not yet improved enough from when you first started this thread, I would suggest pushing it back to the latest test date for this cycle at least (September 14), but you would be best off taking a gap year and taking more time to study. I took my first test when I was VERY unprepared, and I got a 495. I was able to take in again and do better, but it was discouraging (not to mention it really hurts your bank account to pay for 2 $300+ tests). Save yourself the pain and take it when you are really prepared.
Best of luck to you! Remember to relax and know that everything will work out eventually.