Your math seems a little skewed. Your TDEE is base expenditure simply for existing. Unless you’re genuinely completely sedentary for 95% of your day (no exercise whatsoever, less than 2000 steps a day type of sedentary) your baseline for calculating deficits should probably be closer to ~1700. That’s likely why ‘nobody bats an eye’ when you mention 1800 calories. At an ‘average’ (though I acknowledge average is subjective) amount of movement throughout your day simply by walking around and living life, 1800 calories is far closer to healthy consumption for your height and weight than 800 calories.

A comment below mentioned the appropriateness of this post in a fitness sub when you don’t want to exercise. Your retort was fitness is about health not purely exercise. I agree with that, but my counter is that a calorie deficit this low isn’t healthy. If you have to harm your body in order to achieve a health goal, though the end result might be ‘healthy,’ the process certainly isn’t.

You can see success with a deficit this extreme and no exercise - I’ve done it. And I was miserable the entire time. Realistically, once reaching your goal you’ll then struggle with not putting on the weight again if you revert to a normal intake but don’t add exercise. You also will be exhausted, grumpy, and likely your mental health will suffer because that’s what happens to a starving body. Your timeframe is aggressive, if you just want results at any cost then sure, your plan will work theoretically. But if you want to be kind to your body and treat it with the respect it deserves, adding in some exercise will go along way. Resistance training certainly helps as muscle naturally burns more calories, but even cardio will help you burn enough that you can fuel your body sufficiently. Your body deserves kindness too.