Neoblader: it would be best if you didn't put down anything about accelerated classes through tutoring. Get in first, and then in yr 10/11 you can discuss with your teachers/year adviser or whatever, your subject selections. (i.e. by working around what you've got if you've already done an hsc...
if you were to get 70% of all questions right in the actual umat, that would be an excellent result. (i.e. >97 percentile, depending on how they distributed marks per questions)
personally, if you want to practice certain topics ahead of time, i'd be practising topics which schools don't teach that well and which can take a longer time to grasp. topics include circle geo, probability/counting, maths induction.
in this scenario it would be best if you looked at the atar of the dux in the past few years to get an indication of where you're headed, if you were to rank first in everything you could get 99.95, but realistically if you keep working hard you shout get high 98's-99.