craigfrogers

Dcf isn't an option in Australia

Yes as Transborderwife says CR-1
Here are the guides:
http://www.visajourney.com/content/i130guide1

K3 is defunct.
CR1 is the only option.
As it has already been 2 months, I think you can apply for DCF (direct consular filing) if you stay there for 4 more months, but I am not 100% sure. I think Australia allows it. DCF takes around 4 months.
If you can initiate DCF even after 4 months, it will be much faster than CR-1 which is an extremely slow process averaging around a year.

And forget chasing a K3, I have actually seen cases where filing the I129F has slowed down approval of the I130 petition
Getting a CR1/IR1 is done via the same process, you will automatically get a 2 year GC if entry is before your second anniversary and 10 year GC if you enter after your second anniversary
The best way to speed the process up is to have all your paperwork in order and especially at the NVC respond as quickly as possible

IF DCF is available in Australia, then the USC would have to be a legal resident of Australia to qualify....his post seems to indicate that he is currently living in the US and therefore this is not an option

Also, for clarity you will submit an I130 petition. Make sure it is complete and includes all required forms and supporting documentation. After the petition is approved it will be send to the NVC for processing and you will eventually have an interview. If all goes well your wife will receive a CR1/IR1 visa stamped in her passport.
And assuming your wife is an Aussie citizen, she will be able to visit you on the VWP during processing of the petition- we are not all so lucky

Cr1 is what you need. It'll be probably 8-14 months

If you earned over $10K in any of the past 3 years you would need to file US tax returns for those years. You may not owe tax, but would be required to file. That needs to be sorted out prior to the visa interview to avoid delays.
See the links in my signature below for more information.

You would include a letter stating why you were not required to file an income tax return for the last 3 years. However if you worked and made over the threshold to file, anywhere in the world, you are required to file. You include the joint sponsor as well who does make over the poverty guidelines for their household size. The immigrant will be not be denied for sponsorship as long as there is a qualified joint sponsor as well.
You would submit two I-864 with appropriate documents.

Yes. You need to include a statement explaining why you didn't file (were you living abroad? as a USC, you are still required to file taxes even if living abroad. if so, i recommend filing back taxes). If you did not have a job and are in the US, just include a statement stating you didn't earn the minimum to file.
Not unlikely to get approved, they will look at the joint sponsor's income to ensure that they earn enough to support your wife.
If you do live abroad, you need to prove that you intend to establish domicile in the US prior to your wife immigrating.

Yes. The petitioner is always the primary sponsor.