Hello bridiew!
Most of your subjects are science-based so maybe it would be good to pick up a humanities subject next year, if you want a change in subjects, namely 20th Century History, and if you feel that it's too much for you, you could drop it in Year 12 and pick up another subject, such as Further? Also, when you say that you can't see yourself moving into 3 4 revs or global, you're still in year 10, so perhaps next year when you're well into the subject content, it would make you feel more comfortable with picking it up in Year 12. Also, next year, it's likely you'll have a greater understanding of what the humanities subject entails and what skills it requires for you to do well.
I don't do Further but my friends tell me that it's really easy to manage, so if you're worried about History taking up too much of your time, you could select Further instead?
The only undergrad pathway for Medicine in Victoria is through Monash Uni's Medicine program and I'm not completely certain but I'm pretty sure Monash doesn't offer breadth subjects (please correct me if I'm wrong), however Melbourne Uni does but there's no undergrad Medicine Program there, only postgrad Med.
Above are just some thoughts but I think it's mainly weighing up the pros and cons of taking each subject next year and what options we have if those don't work out.
Hope this helps.