Matt and Ângela

My wife had her interview this morning, scheduled for 8:00AM. Basically the same story, she got sworn in at the 10:30 ceremony.
 
However one important additional piece of information -- to reduce the number of people in the building, they are only letting in individuals who actually have the appointment, so I could not enter.
 
I left to go work in a coffee shop, but then realized that today was the first day of all restaurants/coffee shops being takeout only. So I worked from my car for a couple hours until she was done, and I did not get to see her ceremony. 

An update for those following this topic -- I just checked our case status online, our I-131 and work permit were approved yesterday!
So in case anybody else runs into this in the future, to answer my original question about how long does this kind of thing take to resolve:
On December 2nd, we received the RFE claiming my wife had left the country. The RFE was dated 11/25 (delay in delivery because of Thanksgiving holiday). On December 4th, our lawyer sent back the response. It contained a sworn statement from my wife that she had not left (with wording from our lawyer), a copy of every page of her passport, a printout from the US Government's I-94 status page showing no evidence that she had left the country, and whatever cover letter the lawyer included. On December 9th our status changed to indicate the RFE response had been received, and case was going back in review. On December 18th status changed to approved. Presumably if USCIS had not made this random inexplicable error, they would have issued the approval instead of an RFE on 11/25. So bottom line, the delay for this was just over three weeks.

An update for those following this topic -- I just checked our case status online, our I-131 and work permit were approved yesterday!
So in case anybody else runs into this in the future, to answer my original question about how long does this kind of thing take to resolve:
On December 2nd, we received the RFE claiming my wife had left the country. The RFE was dated 11/25 (delay in delivery because of Thanksgiving holiday). On December 4th, our lawyer sent back the response. It contained a sworn statement from my wife that she had not left (with wording from our lawyer), a copy of every page of her passport, a printout from the US Government's I-94 status page showing no evidence that she had left the country, and whatever cover letter the lawyer included. On December 9th our status changed to indicate the RFE response had been received, and case was going back in review. On December 18th status changed to approved. Presumably if USCIS had not made this random inexplicable error, they would have issued the approval instead of an RFE on 11/25. So bottom line, the delay for this was just over three weeks.

I do not think he will be able to get a visitor visa at this point if he has K-1 pending. They will think he is planning on marrying you and staying. Of course I am not a lawyer -- just a random dude on the internet spouting off.
It might be worth calling an immigration lawyer and discussing your case briefly. You will get at least some free advice on the phone, and perhaps you could just hire them for a 30 minute consultation or something.
Of course if you do that, in all likelihood you will hear exactly the same things people are saying here. Still, if I was in your position, I would do it.

I just read this whole thread, and one thing that nobody has asked yet is whether you have hired an immigration lawyer? In a case like this where apparently there is going to be a high risk of denial, I think it would be worth the investment to have a top notch experienced lawyer working with you.