Unable to lose weight

I have to admit, I'm confused. I have more questions than answers, right now. Generically, I'd say kick-starting is IMO generally a bad idea, and extreme lowering of calories is pretty much always a bad idea, unless severely obese and under quite close medical supervision for deficiencies or complications. Figuring out what's going on, and adjusting the plan as needed is IMO always a better idea.

How long have you been stuck, and what is the definition of "stuck", exactly? Anything under one full menstrual cycle can be water weight weirdness, rather than stuck when it comes to fat loss, or a month or so if you don't have cycles. Weight loss stopping suddenly after a decent loss rate implies different causes than weight loss tapering off gradually over weeks.

You are set up for an estimated 300 deficit, but sometimes/often eating at a 500 estimated calorie deficit. Losing about 2kg of fat in 7 weeks would imply an actual deficit of about 314 calories daily. That's not far off estimate.

MFP, other calorie calculators, even fitness trackers just give us numbers that would be average for people in our demographic. Individuals vary from averages. Most people are close, but hundreds of calories off is just rare, not impossible. (MFP and my good brand/model of fitness tracker are off by 500+ daily for me, compared to nearly 10 years of food logging and weight change data. My weight changes are quite predictable when I base my plans on my experience, not on MFP or the tracker.)

On top of that, logging can be a somewhat subtle skill, and most of us have face-palm moments where we recognize we've been making some kind of systematic error.

Either of those factors, or a combination, could be contributors to actual loss not matching estimated loss.

Since you don't tell us your age, height, weight, or daily life activity, we can't even roughly reality-test your calorie estimate. Maybe your maintenance calories are actually lower than 2100?

Are you eating back exercise calories, or just eating 1600-1800? Strength training doesn't burn massive numbers of calories . . . which doesn't make it not worth doing, but isn't adding much to your weekly calorie burn. We can't even guess how much, because again your demographic data would be major factors in that estimate. For me, 3-4 hours of strength training might add maybe 490-650 calories per week, so average of 70-93 calories per day when averaged over the whole week.

If the 10-12k steps were included in your activity level setting, they're already accounted for, so not an add-on.

I'd like to help, but it would be easier to do that if you're willing to share more information.

A BMR estimate, or even resting metabolic rate (RMR) measurement (close to BMR, but which would require a sports lab test) isn't a way to ensure a person's in a deficit.

BMR is the number of calories a person would burn flat on their back in bed 24x7, unmoving, in a coma, pretty much.

People not in a coma burn many more calories than BMR from job and daily life activity, i.e. non-exercise activity thermogenesis (NEAT). If they exercise, they burn even more.

TDEE - total daily energy expenditure - is a relevant estimate. Pre-exercise calorie burn, loosely NEAT + BMR, is the estimate MFP uses as a basis.

Eating below BMR would be a deficit, sure . . . but for most people, a much too aggressively extreme one, unhealthful and unsustainable.

ETA: 4-6 weeks' trial of a calorie estimate and activity regimen is the best practical way to know whether a person's in a deficit, and estimate how big that deficit likely is. Women with menstrual cycles would best use full cycles to estimate, to compare body weight at the same relative point in at least 2 different cycles.

If you run away hurt anytime someone correctly (and gently) explains errors, implied or explicit, in your comments, I don't foresee a long residency on the Internet for you. You were trying to help, but if OP ran with your suggestion, they would not likely improve on their current situation, and might waste a lot of money in that futile effort.

Nah, don't go away. Comment, read, think, learn, comment some more.

It's just a terminology thing, not something dire, and my comment was not intended as a personal critique of you. I was simply concerned for the OP, because we do see people here thinking they need to eat below their estimated BMR, and it's a risky thing to do in many - maybe most - cases. Faster loss isn't better loss, and can be unhealthy.

Your underlying concept, checking other estimating tools, is a good one. I agree with it. The same kind of idea was behind my PP in this thread, saying that there wasn't enough info in the OP to give solid advice. Having the person's demographic data would let us consider that aspect.

Generally, I think we're on the same page - making sure there's a deficit. I hope you'll keep participating here, sincerely.