You can work out how ftb and child support interact if you go on the human services website and do a family assistance and child support estimate. It will ask you for an estimate of your income, your ex partners income and then will work out what ftb and child support will be (approximately). It will also take into account any shared care (if that is happening).

Mega is pretty much bang on. You have thirteen weeks to contact child support. My suggestion would be to make contact with them as early as possible though as they will only assess you from the date you contact - so you may be entitled to child support from the date you seperate, but they won't take into account the date you seperate - just the date you contact them