A syllabus or guidelines is pretty much absent. You are pretty much expected to learn all the concepts from the lectures and apply those concepts in exams (unless other specified).
A lot of units of study don't release past papers because they tend to re-use them. From experience, maybe <20%...
I don't think it's possible to buy a digital copy.
As a publisher, Microsoft have really fallen down in respect to making their games available digitally.
4 unit maths is overkill for the Economics component, but having that mathematical background is more than enough prep for that side of the degree. For engineering, absolutely.
The following link outlines what the Honours program in B. Eco entails but I'm sure it's fairly similar across all universities which offer this major:
http://sydney.edu.au/arts/economics/undergrad/honours.shtml
The second major you choose is really up to where your interests lie.
It's...
Also see if you can ask the other teachers for advice.
Theoretically, there shouldn't be a discrepancy between marks as they are using the same marking outline. If you think your teacher is an easy marker, I wouldn't bother asking for help from them.
I haven't heard anything regarding the job market being saturated. It's likely that graduate prospects are fairly average if you take into account all the different fields an undergraduate can enter into.
If you want to make sure that you're competitive, I would recommend aiming to do honours...
In contrast to HSC Economics, it's much more mathematical. You'll also learn a lot about econometrics which is arguably the most important tool an economist has in their tool set. The maths itself shouldn't be too difficult if you've only done two unit. Differentiation and integration would...