Seeing as the test does get harder and harder each year, it's very difficult to get a good idea of what marks you will need to get a certain score.
Keep in mind that the superior, above average, high average, etc. marking terms refer to your performance relative to your peers, with superior meaning that you are in the top 11% of scorers in that particular test. As you mentioned, these scores vary greatly between the 5 exams; a 60% could get you a superior in numerical reasoning but only an average in reading comprehension (
for example). The 'cut off mark' is entirely based on your
relative performance to others sitting the test which is then used to guide your result (Sup, AA, HA, etc.)
The marking schemes are very much out of our hands, with factors like the 5% rule creating different levels of competition between schools as well. I would say that the best thing to do at the moment is to just keep setting goals and keep on improving your own performance when completing practice or studying concepts to increase your chances of achieving a superior.
In other words, shift your focus from 'achieving a superior' to 'performing your best on the tests'. Ultimately, this is the only thing in your control.
If you haven't seen it already, this forum (
https://atarnotes.com/forum/index.php?topic=155074.0) has some great advice.
Best of luck!