All US citizens need to file returns with the IRS, so show the Equivalent dollar amount made last year at the Australian job that was reported to the IRS on that line. As for current employment, list current job.
http://www.irs.gov/faqs/faq13.html (Filing requirements)
http://www.irs.gov/faqs/faq1-6.html (How to get IRS transcripts to use)
Also needs to show domicile in the states, a parents home is OK. And probably will need a co sponsor unless he is just transferring back to the states and has a job waiting for him in the states.