I pay money for a service. I have a contract - written or implied - with the provider of that service.
In this case, my opinion is that I have a contract with BYOJet for the provision of tickets for flights to Dublin from Melbourne on specific dates and times with
Etihad. I have agreed to accept minor changes without recourse, and to have the right to veto major changes. That's in their terms and conditions. The airline has now cancelled the flights. The travel agent is unable to provide the service, therefore they are obligated to refund me. Without penalty. If they feel they've been dudded, they can take it up with
Etihad or the Australian government, because it is their actions who have cost my travel agent, not mine. I won't accept a credit minus some booking fees, with an airline that may not exist in a few months, and for an amount that may not pay for a future flight.
You seem to completely disagree with this characterisation. That's your prerogative, but I don't take legal advice from randoms on the internet. I'll let me credit card provider, my travel insurer or the NSW small claims tribunal sort it out.