It's never too late to start now, even if it is just 1-2 months till exams! Truth is, you will get a better score if you start now rather than never start. I'd definitely recommend you talk to your teachers about your situation and whether or not they can provide any resources to help. How I would start in your case is firstly familiarising yourself with the content. This can be done through note-taking, teaching the content through others, creating summary sheets, posters, you name it! Choose the one most efficient for you as a learner. Once you've done this, start your practice exams. These will help you identify and fill the small gaps in your knowledge in time for the exam. You don't need to get a crazy amount done - just enough to make you feel confident going into that exam. Ensure you correct your practice exams though - there's no point in doing them if you don't correct them, since that's the only way to learn from them.
Before you begin practice exams, it could be worth it doing checkpoints or textbook questions to consolidate your knowledge. I'd recommend creating a checklist of all the things you struggle with from each subject and revising those. There's no point revising topics you are already confident in - it's just wasting your time. Try studying with friends as well; it's a great idea to form a study group. This doesn't just help you feel more motivated, but it also involves sharing ideas, knowledge and a perspective you may not have heard. Another good way to revise is to create a little summary for each point in the study design. This will ensure you know everything from the study design! Don't hesitate to ask your teacher for help if you don't understand something. You'll be grateful come exam day. I always, always recommend asking your teacher for ways they can help out. I'm sure they'll be more than happy to.
If you feel the need to procrastinate, a good motivation reminder always works. What motivates you to get (x) study score or (x) ATAR? Is it a dream career, uni course, or just doing your best for your personal fulfilment? When you sit and think about your goal, it may not seem so unreachable. Personally, it often makes me get straight to work and spam some practice exams or just revise. Even just light reading before bed can help out. If you do find it difficult not to procrastinate, then block everything you use to procrastinate. If it's an app, delete it. A website? Block it. Your Xbox? Ask someone in your family to hide it somewhere you'll never be able to find it. I'm never a fan of totally removing something you like to do to study, however things like gaming can often be counterproductive so it might be best to remove it fully just for these 2 months to really focus. Things like drawing, reading or exercise are better things to use to relax in between study sessions.
You've passed all your SACs for your subjects - that's really good! You're already halfway there. I understand your frustration, but the best thing you can do is use learning and revision techniques to build and strengthen your foundation before doing practice exams. I know of people doing only 1-2 practice exams and getting scores in the high 40s. This is because they have a very strong foundation in their subject. This may not work for some people, however it is possible. As of now, don't worry about practice exams (except psych! you seem to be doing well in that, so do practice exams for psych!) for your subjects; rather, focus on strengthening your foundation, then doing practice exams. It's really important to build this foundation now, and not leave it till later and delay it.
As for burnouts, you won't, if you relax in between and take things slowly. Remind yourself that you can do this! Also, if your planning and organisation involves creating a study schedule, it's normal if it doesn't work. Most people find it seemingly impossible to keep a study schedule and follow it in the long-term. I think it is more productive to write down a list of things to get done for each day. It's especially satisfying when you tick or cross out each one and you've done the whole list. It's a reward in itself!
Good luck!