Update: I had my interview on the 18th of December. It was about 10 minutes long. He was originally quite stern and then as soon as we sat down, his mood shifted and was laughing along with us. He asked me probably 6-7 of the questions from the I-485, we did some corrections and then he just asked me and my husband some questions about our marriage. I did read everywhere that they separate couples in Louisville but we weren't separated. He said it was the easiest, quickest approval of the day. I was on cloud nine walking out of the building. I got my official approval the day after and my new SS has been delivered too.
If anyone comes across this and has an interview coming up, please don't be worried. I still don't know why I was called in for an interview but I'm glad I got one in the end. Happy Holidays!!