Hi @GlenAlvie, welcome to the forum. Sorry to hear what you're having to go through. I don't have any experience with it myself, but I've hard similar stories from other people. It's hard to imagine how difficult it must be.
I did find a few online resources that may be helpful. You've probably been trough it all already, but there maybe something.
https://mothersofsons.info/false-accusation-charges/defending-violence-orders/
https://astorlegal.com.au/false-avo-claims/
https://justicefamilylawyers.com.au/avo/how-do-you-defend-yourself-against-an-avo/
https://lylawyers.com.au/blog/false-avo-claims/
I realise they're all lawyer websites and you did say the cost of defending yourself is a major issue, but there may be some ideas in there about what you can do and what you're rights are. I'm going to assume a lot of the options involve lawyers. Which as always, make it impossible if you cant afford them.
The best of luck to you.