Calorie burning and weight loss

Hi! In the past 7 months I lost 35 lbs, going from 145 to staying between 110-115 at 5”3’ and 22 years old. I haven’t always done it the healthy way and for a bit I was at 105 which is basically underweight. So I’m trying to be healthy about it. I am good on diet. I try to stay within 200 calories a meal now. I was just doing cardio, running on average 5 (sometimes as much as 8) miles at least 4 times a week and eating once a day, very low calorie meal or every other day to maintain that 105. Now I want to maintain the 110lbs. So far it’s working, but now I’m running 4 miles, which according to my Fitbit charge 3 I burn between 380-400 calories depending on how long it took me, and then i head to the gym and spend 45-60min doing HIIT and keeping my heart rate up. For an hour it said I burned 380 calories yesterday on my Fitbit. I have been doing the 4 mile run then go to the gym for 45-60 minute combo 5 days a week. Just wanted to see if you guys thought this is enough to keep my weight down fallowing a mostly strict diet of 200ish calories a meal (3 times a day) with once or twice a week, maybe having a pizza for a meal or something of that nature. Also, do you think my Fitbit sounds accurate with calorie burn? Note for the gym I do focus on keeping heart rate up and monitor it while I’m working out to make sure it doesn’t get to low. For the running I don’t monitor heart rate but it says it’s pretty high, and I never walk any of the miles I run and run a lower 10 minute mile consistently.
Sorry I know this is long but it’s bugging me. Thanks!

600 calories a day?

You cannot be serious.

200 calories per meal is incredibly low! Whilst you will lose weight on these calories, your body will not be functioning well at all. Your body will also release hormones to make you crave food to bring you back to your original weight. Weight loss should be very gradual to prevent this, and you're doing an awful lot very quickly. Ensure you're fuelling your body, be patient, and focus on making your body more capable rather than smaller!

And, just so you don't think I'm making this up off the top of my head: I have a 1st class BSc (Hons) degree in Animal Science, with a heavy nutrition bias, I'm a competitive powerlifter who has to fluctuate my weight regularly in order to lift well and also make my weight class, varying from 68kg to 58kg regularly, but doing so in a controlled manner. I have also helped 2 friends with healthy and sustainable weight loss, losing 50kg combined, but never hungry or deprived of food they love. If I can help any further, do not hesitate to contact me!

I mean, more accurately between 600-850 realistically. But like I said I have days where I ate a pizza or something and that’s blowing 1000 right there. But I’m not losing weight anymore eating like that even with the running and gym combo , of course I was eating way less than that previously too, so it may be a metabolism problem now.