jieunni, possibly in your case it may have been better for you to take the ADFA offer, as you are obviously looking for security if all fails. Look at what you've missed out on with ADFA - free university education and free flying and might I say getting paid for it too.
You should go back now and tell them you'd elect for direct entry pilot. You've obviously passed the RAAF Candidate for Pilot Selection to be selected for ADFA and Pilot Training. Look at all the money you'd save in learning to fly alone. Do a Degree Course part-time whilst in the RAAF or afterwards. The only contraint is the ROSO (Return of Service Obligation) of I think 10 years now and more if you are further trained on the B737 BBJ or A330 Tanker. I can't remember when I was in the military what it was. But, remember, the failure rate is high.