Hi ImmutableObject,
NBN services generally use IPoE, but you could try the PPPoE options too. Unfortunately the setup you have outlined is not supported by BigPond Tech support.
BigPond Tech Support provide assistance with getting the modem back online in the standard configuration. If you are needing assistance with advanced configuration or 3rd party devices, I would recommend that you contact Telstra Platinum on 137 587 or a private computer technician of your choice.
You can find out more about the services offered by Telstra Platinum here: https://www.telstra.com.au/connectedhome/enhancements/platinum