In further maths, you're allowed to take a calculator and summary book into every SAC and exam. There is no such thing as a tech-free assessment in further.
You don't need 100% average in your SAC's for a 45+. Infact, you can get a 50 without a 100% SAC average, and in a very strong cohort, you don't even need rank 1 SAC average.
The reason for this is because some schools give harder SAC's than others. For some people, it might be just as hard to score 80% on a SAC in your school as it is for other schools to score 100%. Also, if you're in the same class as a few geniuses that end up with a 50 study score, they might score higher than you but you could still end up with a 50.
As for the exam, from 50 to 45 it is generally 1 study score lost per mark. So if you are rank 1 in SAC's and you lose 5 marks in the end of year exams, you can expect a 45.