Hey, try to relax. I understand why you'd be super stressed about scoring so low on RC, but remember that RC is one of the sections that requires lots of focus and concentration to succeed on. Lack of confidence alone can lower your score.
Here's a suggestion that I think could benefit you. As practice, try spending 10 minutes reading a passage from one of the RC tests you previously took (that way you save future practice tests for after you are more prepared to take them). So, for example, you could start with Crack DAT RC #1. Start the exam and rather than taking it like a normal practice test, set an alarm/timer on your phone to go off in 10 minutes. Then, begin reading the passage at a normal reading pace (whatever that may be for you). After the timer goes off, write down somewhere how far you were able to read (i.e. I read 10 of 14 paragraphs in 10 minutes). Try practicing this for 3 passages a day without actually answering any of the questions. It is crucial that you do this every single day to build your skills (would only take 30 minutes a day).
As you read, I encourage you to....
1) Be sincerely interested in whatever you are reading. Try to learn something new. This is really important because it will help you stay focused.
2) Don't panic if you aren't able to read the whole passage in 10 minutes your first few attempts! That is why you practice.
3) Try to map out the passage in your head. What do I mean? Basically, try to understand that there is structure in every passage you read. Every passage is organized. Perhaps its a story, or maybe a list of experiments, but just try to have a basic idea of where each main idea is talked about.
This may seem kind of silly, but I think it will help you be more comfortable by realizing that 10 minutes is actually a fair bit of time to read 75%-100% of a passage, and it allow you to improve your reading speed and comprehension. Make sure you add this as part of a schedule (i.e. do this everyday from 10-10:30am for a six days). You could do this for longer if you feel you are still not able to get at least ~75% of the passage read in 10 minutes.
Once you feel fairly confident in reading almost the entire passage in 10 minutes, try taking another full length test. Remember you are going to give yourself 20 minutes per passage TOTAL. That means 10 minutes of reading (stop after 10 minutes no matter how far you get), and then immediately go to answering questions for 10 minutes. This will be hard to adjust to, but just keep trying! I promise you that if you commit to doing a RC test everyday or every other day until your exam, you WILL improve. Also, there are lots of other strategies besides the one I provided here. You can test those out too. I have just found that actually reading the passage is most successful for me, and searching for answers puts me in panic mode. Best of luck to you!
Edit: Also, I just noticed you posted that you have to go back to the passage when you answer questions even after you've read it. This is normal. I highly encourage you to go back to the passage to find the answer after having read it. The point of reading it is to know where the answer is faster than if you hadn't read it 🙂