I would do what it takes to lower your cortisol - you're doing several things that raise it by themselves - and combined, I'd say you're in a situation where you're chasing your tail. I'm surprised you're not gaining, honestly. It sounds like you've lost muscle, as well, which affects overall metabolism and body composition, of course.
My opinion is that you're doing several things to raise cortisol, which loves to help us store fat and water and adversely affects thyroid hormone conversion. These effects are seriously underappreciated, if you ask me. I've read it countless times on this board and others after learning the hard way, myself - despite many valid warnings, which I ignored. These things separately are cortisol raisers:
Low carb (without refeeds - I am only guessing, of course)
When combined, they're even worse. They have synergistically crappy effects. Muscle loss is basically a given. Your adrenals are having to fight to keep your blood sugar from tanking since you're likely in a glycogen depleted state 99% of the time, for one thing. You're overtraining while underfueled - lacking in both calories and sufficient carbs, then adding fasting to the mix, which makes blood sugar control even more of an issue. It's extremely rare for a body to be able to do this for a prolonged period and lose weight - and, as I said earlier, it's a wonder that you're not gaining yet. Hopefully, you can turn it around. Hang on for dear life to the muscle you have left.
Anything that's bad for our overall health because it is hard on our body when done for a prolonged period of time is going to affect the ability to lose fat. It will also have a negative effect on sleep, which greatly affects our ability to lose fat for several reasons.
I'd start thinking about dialing it back and not going to such extremes and always focusing on getting an optimal amount of sleep. (Do you wake up between 2 and 4 am often?) If you insist on continuing to exercise as you have been, gradually increase your carbs slightly - maybe go up by 20 g/day tomorrow and stay there for a week, and then up another 20g next week. See how you feel at each level and what the effects are - not on your weight, but on how you feel. The weight loss is a byproduct of a healthier metabolism. I would definitely increase your calories above your RMR, though. Take a good magnesium supplement before bed. Drink enough water and be very generous with the salt.
An overworked, underfed, under-rested body is just not going to give up fat stores without a fight - a fight that may result in gaining. Just my two cents, of course - but I've been researching this topic A LOT over the last five+ years and I feel more strongly about this angle every day. Good luck to you!
Life is not a matter of having good cards, but of playing a poor hand well.
- Robert Louis Stevenson