Went thru the process 4 years ago. Filed for visa here in Florida. Fiance made app thru SD. Took about 6 months including two trips ato SD for interviews. I agress with the proof aspect. Take lots of pictures, recipts etc passport stamps etc. After we got the visa had a six month post wedding interview in Miami then a year later finally got the ten year visa after another interview in Orlando. Good luck.
Waiting outside the consulate in SD reminded me of pictures of the last days around the US embassy during the fall of Saigon.