From my knowledge the exam is worth 50% of the study score and the unit 3/4 Sacs are also worth 50%. (25% each obviously).
There is a lot to remember in legal studies, but if you study consistently throughout the year as your SACs approach, it will all just come back to you at the end of the year. I personally didn't find it very hard remember information. The real trick in legal studies is to understand what the questions are asking you to do. For example, evaluate wants strengths and weaknesses.
I got tripped up in a SAC because the question asked me to 'critically evaluate two strengths'. I saw the word strengths and wrote only on those and forgot about the evaluate part. So that's the real trick, me thinks.