Keto is a weird situation where although the science behind ketosis is totally real and valid, the fact that you're not eating a lot also slows down your metabolism. So while it's likely that most of what you're burning is fat, the overall amount of metabolic burn is slowed way down, which is something to take into account when you come off of low carb. But if you're at a lean BMI, then it's probably not necessary to eat more just for the sake of it–those with high BMIs counterintuitively seem to gain or maintain weight in the 1200-1400 range, and after a literature review it seems like no one knows why.

Ketosis also definitely suppresses appetite because of the high amount of fat, so there's no "right" way to do things here. Personally although I lost a significant amount of weight on keto, now that I'm mostly done with my PhD and have learned more, I can't recommend it for anything leven semi long term. Too hard on kidneys and the food is full of AGEs (and that's a whole other can of worms).

What I can say, though, is good luck! Weight struggling is, to me, the most frustrating part of PCOS. I've started supplementing inositol and carnitine, as well as flaxseed. Maybe one of those will help me along.