That's what an accountant is for. I just summarize my shit and do my log books then give it to him and they do the rest.
In terms of what I get back on the car side of things, it can be around 92%...
I'm not sure Re: ABN, someone will know. I would assume you would need to prove you some how need your car for work related things, which I'm not sure how you would.. Plus you would need to be working on a work contract base, using your own ABN. With the business name thing EG: Your setting up what would be a "business" I guess.. Be more effort for what its worth, plus you would have to show figures.
I'm no accountant, I only know about my own case, so unless you get into property I'll be no help to you.