rajbabu

No, you do not need priority date at all. Be assured.
After USCIS approves your I-130 (called NOA2 typically), they will send your case to NVC. Then, you can call NVC to find your "case no" and receipt no. Case no is everything after this.
The final stage prior to interview is filling out NVC. In order to do, you need "receipt" and "case no". Priority date not needed at all. Check this out: https://ceac.state.gov/IV/Login.aspx . All they ask is case no and receipt number.
Remember again, you can only get these after your case completes in USCIS.
I know it is a nerve wracking process. I had my interview but have not received my passport back. Have not seen my wife in person in a while

Not at all.
Both my wife and I were living in my home country (i.e. outside of the states) during our I-130 process.
We did not receive a single piece of paper from USCIS or NVC and we were fine. We received the interview letter (P4) but we had already gotten a PDF version on email.
My point being: don't worry about it at all. Once you get NOA2 from USCIS, they will automatically forward the case to NVC.

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.

1) no. Normally not until the visa is granted will you know the a#
2) you dont need it at this time
3) no.