Mudrat,
I have no idea why you failed. Maths is not my strong point, in fact I had not even completed year twelve when I passed in 2002.
You sound far more intelligent and educated than myself. My advice would be to take your time before sitting the tests again. I know people who didn't start ADF pilots courses until their late 20s-early 30s so you have plenty of time, no matter what they tell you. You could even finish your degree before applying again.
There are a few good books around to help you with the individual tests. I have one called 'Military Flight Aptitude Tests' that is availlable from Concept Aviation Supplies in Bankstown.
http://www.conceptaviation.com.au/
I have also seen another publication and even a short course advertised in 'Australian Aviation' magazine(I think it's called 'So you want to be a pilot').
Think about if you really want it before you sign on the dotted line. If you fail BFTS you may find yourself stuck in the RAAF for a long time, flying a desk or digging gunpits. Plenty of oportunities exist outside defence if you want to fly but if you do choose to go for it again, give yourself the best possible chance
.