You should do as many units as you can comfortably handle. Since no-one can predict their best 10 units for ATAR, the more units you can ignore the better.
Certainly worth lodging an illness misadventure form. If upheld the Board will use your moderated assessment if it is higher than your exam mark. The Board lets you appeal if your final preparation for the exam is affected by illness.
Awarding one mark for rewriting the question is against the intent and spirit of the marking guidelines. You really need to speak with Michael about this.
I say again, that is totally incorrect.
Here is the official Board of Studies position on the matter:
"Merely rewriting the question is not considered to be an adequate attempt at the paper."
http://www.boardofstudies.nsw.edu.au/hsc_exams/pdf_doc/hsc-advisory-bulletin-2011.pdf
Proven illness doesn't get you "extra marks", you just get your own assessment mark if it's higher than your own exam mark. And no, there are no deferred HSC exams.
I hesitate to criticise another contributor, but that is nonsense. Nobody gets a mark just for rewriting the question (and why would you even waste time doing that). The marking guidelines make it clear what marks are awarded for: responding to the question, not simply rewriting it. Any marker...
See paragraph 10.3.1.7 on page 9 of this document:
http://www.nswtf.org.au/files/20090811_hsc.pdf
In small language courses, for example, there may not be 10% new applicants so the rule cannot be applied.
HSC questions usually ask you to "sketch" a curve, showing the significant features such as turning points and intercepts. You don't need graph paper to do that.
ATAR scaling takes account of the overall ability of the students in that course (that is, the competition you faced in scoring a particular result). So, a 90 in 2 unit Mathematics will scale better than a 90 in General Mathematics.
What the Board of Studies says:
You are expected to provide for all of your examinations:
* black pens (blue is also acceptable but black is easier for markers to read)
* pencils, erasers, sharpener (use pencils where specifically directed)
* a ruler marked in millimetres and...