You do not need 75% of the 400 questions right. There is a curve that they use. Scores are reported between 99-49 but you will only see it if you fail the exam (get less than a 75).
I'm not sure if you need a minimum per section right. The test committee is very vague if you read their pdf about the exam and so most people here speculate.
Study anatomy and dental anatomy really well because these 2 sections don't change much after so many years and I feel like this is where one can max out his points