The encounter at DUB will have been documented and this is simply destined to repeat itself. Faced with an individual who has little or know ties back to Italy, a SO in the USA and who says he's headed to OZ, but doesn't have a ticket or visa for that, OP's SO will simply be denied entry again.

If the carrier is more careful this time, he won't even be issued BP's.

The SO needs to get his visa for the US and OZ and then buy a ticket Italy-USA-OZ-? OP can then buy the same flights USA-OZ-?

Since OZ won't admit either of them without onward travel either, the "?" needs to be resolved as well.

Even with a US overseas consulate issued vise you can still be denied entry if the CBP agents feel that you are inadmissible.

I'm not sure about this.
With a real visa CBP agents cannot deny entry, if I recall correctly.
Visa is granted by a US Consul overseas, which is not lower than an Immigration agent in the decision-making process.
CBP can deny a Visa Waiver Program passenger, hence ESTA passengers.

You do not recall correctly.

CBP agents can and do deny entry to visa holders. They take great pleasure in pointing out that they are DHS and visas are issued by DOS, so they are entitled to make independent determinations of admissability.

Good to know. Thanks.

-UPDATE-

For anyone who has a similar situation in the future and is crawling through old forum posts trying to figure out if they can make it, as I did, I wanted to make an update of what happened.

He decided to get the Australian working visa, and it was issued to him the next day, which was fantastic. He gathered as many types of proof of intent to return to Italy as he could (bills mostly) and I emailed him an itinerary of our plans for the time he would be staying here.

With all this information, he talked the US consulate in Florence, who told him that to their knowledge, it wouldn't be a problem for him to try again.
I also called Border Patrol and Protection and talked to an agent, explaining the situation (without mentioning our names of course) and they seemed to think that he would be okay to cross.

After an incredibly anxious week, with lots of doubts and fears, he finally flew.
His POE was Newark, NJ, which was scary in some ways because if here were to be denied, he would have to fly back across the ocean again....

When he arrived, he waited in line with everyone else, and was of course taken for questioning when it was his turn.
He talked to many officers, each asking pretty similar questions to ones he already answered. But they asked him pretty much everything you could think. They asked about his family, my family, his life, my life, just really grilled him. And he answered everything truthfully and poignantly. He said that they were all very calm and nice about the process, but it was still intimidating. He eventually just told them the whole story, from the first occurrence until now, and in the end, they let him pass. It was such a relief to see him walking out from the arrival area. They even got him his luggage so it wouldn't be circling around and around by itself. They questioned him for about 30 minutes or so, but with the truth and his preparations, everything turned out just fine.

Well done - fairly lucky I'd say. Make sure he doesn't overstay his visa.

That's probably not why they picked up his luggage for him.

Honesty is always the best policy.

Good to hear you get to spend the holidays with him. Thanks for the update.

You are right about that.

If he showed up with 9 suitcases, a pasta maker and 10 kg of espresso beans, he'd be back in Italy.

CBP agents can always deny entry, no matter who issued the visa.

All's well that ends well. ^

No you don't. You need to have onward/return flights OR the ability to prove you have enough money to buy one. When I went backpacking over there I met several people who only had one-way flights.

I don't recall them checking I've had return or onward flights on the two times I visited either. Australia is nowhere near as paranoid about foreigners than the US is.

Actually, the pasta maker would show him to be an imposter. Now, if the 9th bag contained a Nonna to hand make the pasta, THEN he was planning on staying.