It depends on which version of the DAT you get. All the tests are scaled differently according to their difficulty, so if you take a 'hard' version of the organic chemistry test, you can miss a few questions and still get a good score. If you take an 'easier' version, then you have to get more questions correct to get a higher score. They do this to standardize the tests, so it doesn't matter if you take the hard or easy test, you should theoretically end up with the same standard score.
And 3 months is a ton of prep time! You should be able to review everything you need to at least twice.
