I'm in Toowoomba.
Bloody hell isn't on the same level as fuck. It's still swearing but not very bad - a bit above "damn it". The government ran some ads for drink driving a while ago with the tagline "if you drink then drive, you're a bloody idiot" for example. Yes, the ads were stupid - they attempted to get the message across by incorporating mild swearing.
People don't wear khakis. Most people do say "g'day mate" but it probably depends what part of the country you're in as to how many do. Men use "mate" mostly in relation to each other. Women don't really use the word, and you don't really call women "mate". Some do though.
"G'day" is the same as "hi" so it's used pretty frequently. I say "g'day mate" to my male clients, but it is a very casual term so I wouldn't use it with a few.
Sexual partner "mate" in Australian? I don't know, we use "mate" like that, but slang would be something like "she was a good root".