Hey!
Yeah, choosing subjects can be pretty tough

My opinion: you should stick with chem. But that's just what I would do
Why should I do it?
I think you answered it when you explained why you chose it. The truth is that it IS a prereq for many courses at uni, and I think that if you later in the year decide to do one of the courses but can't get in because of chem, I think you'd be pretty annoyed. I know one of my friends decided not to do any maths or science in year 12, because he was aiming to do a course that didn't need either. But now he regrets it, firstly because it seriously limited his options, and secondly because he now wants to do Commerce, which requires maths.
Also, there's no subject that I think would be completely easy, and even those would be difficult to score in, because everyone finds them easy. Have you done Legal or History as 1/2s? It might be an idea to speak to people who have done 3/4. I know a couple of friends who did history ended up studying really really hard for decent marks, due to the nature of the course. They really regretted picking up history because there's so much memory-work. But then, if your memory is good, and your interest is strong, it may be something to consider. As for legal, almost everyone I know who studied it hated it by the end. I know that it sounds interesting, but apparently it's extremely boring. Again, this is just what I've heard.
Do you think the new SD's exam system will be harder than this year? If so, by how much?
Yes and no. Mid-years put a lot of stress on classes. My class didn't finish the course until a couple of days before the exam, and even then we skipped over a lot of material. I personally find end of year exams better because you get a solid month or so at the least to prepare for your exams, and you can choose which to focus on. For example, I found Unit 3 way harder than Unit 4, but didn't have time to prepare for my U3 exam, but had heaps of time for U4. With this SD, you can choose what to focus on based on your own needs.
Also, I think there's been stuff deleted from the SD, which makes it slightly easier. I just had a quick look through it, and there's nothing that I can see that we didn't have to learn this year, and a couple of things deleted. There's more information added, but everything was studied. Since textbooks aren't changing, I guess it can be safe to say there's no significant increase in learning.
It will be harder because you've got one huge exam at the end of the year. But I can't foresee the questions becoming that much harder. Again, it's just my guessing.
How different is it from 1/2?
Quite, except that you keep your stoich knowledge. Other than that, I don't think there was too much similarities. Oh, and galvanic stuff.
I was in a similar situation to you last year; I only grasped stoich. I didn't study at all for chem (or any other 1/2), and resulted in averaging 70-80s. I was freaked out for this year, but then it wasn't so bad.
Chem in 3/4 isn't too hard. Honestly. It's annoying, but not that hard, once you put in your work and understand the concepts. If you choose to stick with chem, pm me and I can give you tips and stuff

Should I just ditch Chemistry for Legal or History?
What would you do if you were in my situation?
Personally, I would stick with chem. I think even though you think it's hard and all, the amount of studying would be less than either of the 2 you listed. When you understand the fundamentals for chem, you can pretty much do any question, and explain stuff properly. But for Legal and History, you need to memorise every little thing they could ask. Again, I didn't do either, but this is from what friends have told me.
I know that people say that you should enjoy subjects and all, but from my experience, you'll end up hating the subjects you think you'd love and tolerate those you think you'd hate. Plus, it's the vce. I don't mean to be pessimistic, but how much can you enjoy sitting and studying? Even for subjects you think you'd enjoy?
Just my opinion - feel free to ask more
