You can do 10,000 questions before the exam, but if you dont understand why you are getting the questions right or wrong, then you are just cheating yourself.
I would suggest to chose 2 sources to study, 1 for content and 1-2 for questions. The Key is to know WHY you are getting the questions wrong. Lets say you get one question wrong due to not knowing the content, read about that content right and there, dont put it off. Have google opened, and read about it, understand it. Once you know why you got the question right/wrong and understand it, move to the next question. The Key here is to be consistent: Study content hardcore 6-7 hrs a day for 2-3 weeks and then do questions every day for 2-3 weeks ~200 per day. You need to be confident that you are going to pass this test.
Everyone gets nervous and its normal, I was super nervous, but once you get to the testing center, know that you will pass, have faith and TAKE YOUR TIME. Read the question twice before you look at the answers, then look at each answer, is this answer giving you the answer to the stem of the question? Does it make sense?