I'm so sorry to hear this.
Firstly, contact Centrelink and let them know you've separated and get things organised there. If you aren't already, apply for PPS (Parenting Payment Single) and change your FTB details.
You may want to open your own bank account in your name only so all your money is only going to you from now on.
Contact either Relationships Australia or Legal Aid with regards to Parenting Orders.

Good luck hun.