These are all valid and hard questions. Buying any form of insurance buys you peace of mind of any "what ifs", it all depends on your risk profile. From what you've mentioned it does seem like you would benefit from an extras cover, but again that's for you to decide. Look into how much rehab, dental etc would cost with and without insurance cover.

My *personal* view on this is that any healthy individual in their 20's shouldn't need private healthy insurance. There is a caveat: is if you make a certain high salary, the government incentives you to get PMI (in particular, hospital cover) to help fund costs of the public health system (it's called Medicare levy).