Barbara37

So you are planning to pay in person at a field office? Then yes, rules of that particular field office apply.

Your husband will need to complete an I-864, for that he will need at least the most recent tax year IRS tax transcript or full tax return and W2s, 1099s, and proof of current income--six months of pay stubs, letter from his employer.  There is no way of getting around this requirement, even with a joint sponsor.  The petitioner is always the primary sponsor, regardless of income amount, and completes an I-864 with supporting documents, even with a joint sponsor, so he needs to start working on this now.  He can file a tax return for 2018 or wait a few weeks and file for 2019.  Sometimes they ask for the most recent three years but one year is a requirement.  Filing a late return for 2018 seems like the best idea in his case.  Any US resident can file a tax return, even if they are working "under the table."  He could also submit bank account statements as proof of income, also he can use assets.  Read the instructions for the I-864 thoroughly.  Good luck!

Your husband will also fill out the I864 and will be the primary sponsor.  Once the AOS is filed, you can use your NOA from that filing to show you are still in a form of authorized status awaiting AOS adjudication.  Some folks send in the relationship documents with the submission (I.e. front loading), as to what is actually required with submission, the I485 instructions point out the details.
 
Good Luck!

1- The USC spouse is always the primary sponsor, so yes, your husband will need to fill out a i864 even if you have a co-sponsor.
 
2- The date your K1 expires is immaterial. What matters is your i94. At the end of it's duration, you will be out of status. Filling for AoS will provide you with a NOA1, which is a document that grants you authorized stay and can be presented to authorities when asked.
 
3- Correct, even though some people send evidence with the AoS application (when they have things worth showing). But yes, all you need for the application is your marriage certificate and the other documents listed in the application.

Alright, I will take some spread out stuff with me, but not a huge amount. Thx for all the info

I would just verify that it says ready on ceac before you schedule. For the most part, you can sign up for an interview pretty quick. They're typically on Tuesdays.
The attached topic is pretty helpful and up to date. A lot of us have also left consulate reviews and other helpful hints on our timelines.