Yes thats what i thought aswell... But seems to be that u and i are the only ones that think that :/ ?
Are you sure they will drop you?
You need to pick it up in the HYE to convince them that you can do 2U maths, make sure to improve your algebra skills and interpretation, because that is essentially all of what 2U maths really is, there aren't any tricks or clever things you need to find, its just being able to cleanly execute complex algebra neatly and interpreting the question.
Do some of the past papers on this site to help get better.
Also to estimate your ATAR you need to post school rank and subject ranks, since difficulty of internal tasks can't really be directly measured your marks mean nothing whatsoever.
If you come 15/30 with 40 and get good in the HSC, you will do alright overall. (for example)