You got a 221g which is technically a refusal and the CEAC status will often change to "Refused" while they process the receipt of the documents they asked for. The case type changing to "Nonimmigrant" happens to every K-1 Visa case before the visa is issued because it is a Nonimmigrant visa and has to be issued by the NIV section at the embassy. It says the case was updated on the 21st which is good - It means someone is touching the file. Stay strong and watch your emails - The embassy will notify you if anything else is needed
Nathan we went through the K-1 process so we didn't upload docs to NVC however we have close friends that recently got a 221g at the interview because the embassy wanted an Advisory on Marriages (CENOMAR request that results in them finding a marriage on record) from the beneficiary AND petitioner. I would recommend logging onto PSA Serbilis and ordering a CENOMAR for each of you and have it delivered to your wife to take to the interview with her. Everything else you listed that the NVC asked for is what they were asked for and the only thing they were missing was the AOM at the interview. Also make sure you have listed all your wife's social media. They are really cracking down on that.
Most cases do involve filing the N-400 while the I-751 is still being "processed" (left in a pile somewhere) thus forcing USCIS to adjudicate the I-751
Make sure you bring the original letter with you on any international trips or you may encounter problems being allowed to board your return flight back to the US
1. Put the actual start date of her residence
2. If you have a Passport and put your Passport number in the "Passport Number" field, you leave Item #48 "Travel Document Number" blank. That item is in case you don't have a passport but do have an alternate "Travel Document" issued by a government. "Country of Issuance" is your home country not the location where it was issued.
I've read about this happening in other forums.... It looks like someone called the incorrect payment amount to USCIS's attentionand they have been rolling out 2nd receipt notices over the last week or two
For the photo evidence, we inserted 3-4 to a page on Microsoft Word, added a text box underneath each pic (to describe who, what, when & where) and then we saved a copy as a PDF for ease of printing out / uploading
I'll add a suggestion here - Use the Public Inquiry form at NVC's website below. It generally gets a faster response than regular email.
https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/ask-nvc.html