Welcome, both of you.

danioj - These aren't Australia-specific answers but...

No one is going to agree to transfer funds at a fixed rate in advance. You will have to accept the rate that is current at the time you transfer. If that is totally unacceptable, and you must transfer funds to obtain your visa, you are probably out of luck.

As far as the debt goes, do you have an Australian credit card? And have you asked the company about a balance transfer? If they can't do that (there will be fees, of course, and no guarantee of the exchange rate), then you may need to pay it off even if you don't want to.