Eas is 3 extra points I believe. If your ATAR is not high enough for the course you want and your principal believes you have the ability to do well at uni your principal can recommend you. http://www.canberra.edu.au/principals-recommendation
Your subjects except for Physics are poor scalers so you must work hard to get good marks in them. However 90 is not that high and is easily doable if you work hard.
North Sydney Boys Mathematics 3 Unit Past Papers
I have decided to post up North Sydney Boys Preliminary Past Papers. Some are missing, especially Assessment Task 3 (because teachers didn't upload them).
Rep me if I helped!