If I understood your first question correctly, the answer is yes. A 72 WAM would comfortably allow you to receive an offer to the Bachelor of Science. In terms of applying for the Bachelor of Science, you will need to apply through UAC after you complete your Prep Program. It will be the same process that you followed when you initially applied for the Prep Program, although you will not need to submit a personal statement or attend an interview. Instead, you will simply include your transcript in your UAC application, which will be used by UNSW to assess your application for the Bachelor of Science.
Regarding the 60 WAM requirement, you will need to achieve an average of at least 54 in term 2 and term 3 in order to achieve an overall WAM of at least 60. With that being said, are you sure that you need a 60 WAM for the Bachelor of Science? If you found this number on
this page, then it does not apply to you because the Internal Program Transfer is aimed at UNSW students transferring internally. Additionally,
this document states that
"admission to the Bachelor of Science degree at UNSW is based on successful completion of all 6 courses." This is unlike equivalent documents for the other fields under the Prep Program, which mention a minimum WAM requirement.
I hope this helps!