You're gonna be okay.
Just a little word of encouragement from the other side. Last summer I was in your shoes. I hovered at around 50% or less on multiple choice questions most of the summer. I was up and down all the time and never felt truly comfortable with my scores. I took the Themis simulated exam and got about a 40%. I cried the rest of the night and was sure I was doomed. I wasn't. I just kept going, and even though I never felt fully "prepared," I took the exam and passed by 7 points. Not by much, but who cares?
Now, I'm working in a job that I really like, with a good boss and coworkers, and I'm proud of myself. If I can do it, you can do it. It gets better, I promise.