Is it too late to change the date of the test? I remember reading that there is a fee to do this, but I don’t know when the deadline would be.
Have you taken a practice exam, preferably a released past test? If you have, and have scored a 600 (or less than you want), I would absolutely not take the test. It is better to lose the test fee than to take a test that you know you will not receive the score you’re shooting for.