in terms of scaling, ur subject ranks like this (from best to worse):
Maths Extenion 1
Chemistry/Economics (similar scaling)
Biology/ Legal Studies (similar)
English Advanced
Ancient History
Business Studies
Environment Science
Fixed.
Also, one shouldn't just look at the mean scaling. Most of the time, the bottom end of a subject really drags the mean down despite awesome scaling at the mid-higher range (where most people would be aiming) and it also doesn't take into account whether or not a subject is capped (or how much it is capped by).
@ OP - Your subjects look fine load and scaling wise. With 13 units you might find that some of your efforts/time is being wasted and if so, i suggest dropping business or whichever one you are hating/performing the worst in.
With your back ups, i suggest you steer clear of EES unless you absolutely love it and are adamant that you are going to ace it. And when i mean ace it, i mean absolutely rip the exams apart.
If you are not aiming for a super higher ATAR, just pick a mixture of subjects that you love and are good at (and you can ignore what i said above). Remember that you will most likely perform better in subjects which you like