Your marks “balance” thing isn’t actually how the internal HSC mark is calculated. Under your logic, someone who gets 50% across all school tasks will get an internal mark of 50, with a maximum HSC mark of 75 (if they get 100% in the final exam). This is not how it actually works - read up on moderation to see how NESA does their stuff.
The information that the BoS tends to ask when predicting atar is your marks, ranks, school rank, and number of band 6s in the subject from previous years.
From the given data, I’d say mid-high 70s (not enough info to be accurate) but if you work hard and keep the ranks up, an 85+ is achievable. Maybe focus on business studies and maths because they tend to be “easier” marks than the other subjects.
What uni degree do you want to do? Keep in mind that you might not end up needing an 85+ to do it, so don’t get too hung up or stressed out about attaining a certain mark.