If you're at the interview part of the process and only just now asking about this, I strongly suggest you (the US citizen) do some serious research on the requirements for the K-1 and AOS.
My guess is that means she's not getting an immigrant visa anytime soon, and that she is in administrative processing. This can take days to years. All she can do is wait.
Either process will take around two years for her to be able to immigrate.
Start researching and reading as much as you can. CR-1 would make the most sense. Also research CRBA.
Very very unlikely she would be approved for a B visa.
No, you cannot use the joint sponsor's car as an asset.
You need to either have your wife find a better/second job, or find a different joint sponsor. Your numbers are borderline, and I can't see you being approved.
US immigration is not quick, cheap or easy. I suggest you read the guides and start researching. Entering the US with a tourist visa with the intent to marry and stay is fraud.