So the reality is that we can't cheat physics. I want you to remember this both now and after your surgery. While I can't make an super accurate assessment of your total kcal expenditure per day right now, I'd guess it's probably in the range of 3000 to 4000 kcal per day based on your current weight.
I'd also guess that your total intake right now is around 800-1000 kcal. This means you are absolutely burning massive amounts of fat currently.
So I know you're thinking if that's true, then why isn't it reflected on the scale? The short answer is scales lie. They only show total weight, but as you alluded to above, our bodies are made up of lots of "stuff" other than fat, so scale weight can vary widely just based on how hydrated you are, how much glycogen you're storing, and the weight of your stool.
In short, trust the process. You'll be fine.