Sorry to hear you are having to go through this

Definitely open your own bank account and get a PO box for your mail only. Try and save some of the money that he puts into your spendings account and move it over into your own bank account. You might have to withdraw the cash first then deposit so there is no trace that he could see. If he asks about the cash withdrawals just tell him it's for groceries, etc.

Talk to centrelink, you never know there might be something you're eligible for.