Also, if I do end up picking up chemistry, would it help me in a way with any of my other VCE subjects (English, Further Maths (Year 12), Mathematical Methods (CAS), Specialist and Physics) probably physics the most beneficial.
VCE subjects don't really 'help' other subjects all that much, there's a bit of overlap and related concepts (e.g. calculus, learn about vectors in spesh, use them in physics etc.), but I wouldn't say it's really a 'benefit', more like 'oh neat, these concepts relate together pretty well'.
There's things like in Unit 3 Chemistry, you cover spectroscopy, which relates pretty well to content in Unit 4 Physics. In Unit 3 Chem you also do a bit of protein and DNA stuff, which relates to biology - I don't know what part of VCE bio specifically though (don't get put off by this, it's actually quite interesting). I dunno much about Unit 4 chem, having not done it yet. edit: Oh and the different models of the atoms also relates to Unit 4 physics - overall though, they're slightly different perspectives on things, the main focus for the topics is different.
While things have neat mathematical relationships and that you will be calculating a lot of stuff in Chemistry, it's not a maths subject, the concepts and what's going on 'chemically' is what is the key (you could replace the word chemistry and chemically with physics and physically here too).
In terms of catching up, have a talk to the chem teacher at your school. They might point you in the right direction. In terms of resources, chemguide.co.uk and youtube (khanacademy specifically) might be a good place to start (but you'd need to know what topics to take a look at first though). You're not really disadvantaged at all really, you'd be able to pick up Unit 3/4 chemistry without having done Unit 1/2 if you really wanted to (provided you were willing to work hard to catch up)