Congrats
When my friend’s wife (from Germany) became a US citizen she bought a Glock 19 in celebration. 
Are you guys planning on doing the same? 
Sorry to hear that! I bet you’re glad you don’t have to deal with them anymore! Our experience has been pretty good so far, but I’m sure our situation was different than yours. My wife was in country on a student visa. From when we submitted our change of status application to when we had our interview/approval for green card was only about 3 months. I think that 20 months is a little ridiculous, especially for the fees that they charge.
You can make that two South African’s then…s Just waiting to get my application back from S1 in Juneau so we can submit it to USCIS. They say the process is expedited as ARNG but we’ll see…
As soon as I have my Citizenship I can make a bee-line to get back into Law-Enforcement. 
To the OP, congratulations brother, I know it is never an easy road to get there, but it is a worthwhile one!
Your situation doesn’t differ much from mine. My wife had been in the country since '98 on a student visa and had already completed her bachelor’s and was taking advanced classes working on a master’s I believe.
Her green card interview was just over 4 months after we mailed her application in. After that we didn’t hear anything until her card arrived in the mail 20 months later. Calls to USCIS would yield nothing more than “still waiting on background checks”. Basically laying the blame with another agency.
I wish. I did buy her a 1911 in 9mm to use for self defense around the home when I’m away for long periods of time. Because of the kids we have been able to get to the range together so she can fire it. She has done a little dry firing and practice loading & unloading it. One of the local gun store owners is instructing a couple of handgun training classes later this year. He placed 10th in the Western States Single Stack Championships this year, so I believe that he would be able to provide a good foundation.