Just letting you know a Bachelor of Science from both Unimelb and Monash don't require Chemistry as a prerequisite but you can still complete a Biomedicine major.
I will use Unimelb as an example
Yes, doing science will mean in the first year you won't be doing biomedicine subjects but you will still do the biomedicine equivalent (e.g. bio, chem, maths etc)
But from second year the science subjects are shared between the biomed and science students so there won't be anything to different from your degrees.
Excpet for the biomedince core subjects, which quite frankly are difficult and more stressful.
The 1st year core subjects have changed since I started by degree back in 2019 so I can't comment on that but they look interesting, but the second-year core subjects have an equivalent science version so again you won't miss much.
I'll be honest our thrid year core subjects were very unique and rewarding to do and had a biomedicine focus (e.g. focus on disease, clinical care and research) the subjects were interesting but also challenging. But you won't limit yourself doing a science degree yo u can still apply for medicine (or another health-relevant course) and even pursue biomedicine honours from your science degree!
So if you are finding chem difficult don't worry you can still achieve your career aspirations without it.
Also, when I was in year 11 I was also getting 60s in my tests (and we had in-person learning xd) I think year 12 chem is a lot better the content is more applicable and teachers are more motivated to make sure you understand the content.
Also Unit 4 has a very bio focus AOS 2 is food chem which is pretty much bio (protein etc) so I think you might find that enjoyable.
You also have the summer to prepare for chem which is what I did to feel more confident going in. Either way whatever you decide you won't be limited with your career paths.
Good luck