Need Help Understanding "Net" Calories

Hey all- this is my first post, and it's regarding something that looks as though it confuses a ton of people in this community: the subject of "net" calories. If this is something that has been comprehensively explained in a knowledgeable way (seriously, the amount of folk wisdom and junk science thrown around these parts is staggering, even to someone who is decidedly not an expert in anything) please be so kind as to point me in that posts direction! For now, I tend to be long winded, so please excuse what will probably be a lengthy lead-in to my question.

First, me: I'm a 31 year old Italian-American dude, 5'10, about 217 lbs (down from around 230.) This is probably beside the point, but I'm broad shouldered and densely built with a lot of natural muscle, no gut and little flabbiness even at 230 lbs. I just sort of get big & wide when I gain weight. It's still fat, it just presents itself as a wall, which probably enabled me to let it get this bad.

In service of my desire to get back down to my college fighting weight of 180, I've recently treated myself to a "FitBit", which, as many of you know, tracks calories burned throughout the day. The Fitbit syncs with MFP and allocates burned calories toward my "net" calorie intake.

I'm no expert, but my plan, based on successful periods of cutting/fitness in the (increasingly distant) past, is this: start with a reasonable but restricted calorie diet, mainly dumping carbs, limiting them to around 100G a day, mostly from veggies. I'm basically going for a protein and, to a lesser extent, fat-heavy diet of around 1500 calories, never going below 1300 or above 1700. For now, the exercise I'm engaging in is limited to long, brisk walks, usually about an hour a day, maybe 3.5 MPH, which is easy due to the fact that I live in Manhattan. More long term, I intend to start lifting and exercising more strenuously, which will coincide with increasing my calories while continuing to keep carbs and sugars reasonably in check.

So far, I've lost a little over 10 pounds in two weeks, I feel fantastic- if a little hungry now and again, and envious of my wife's carb-heavy meals. I'm clear headed and LESS fatigued than back when I was eating normally. My digestive process is healthy and normal. Here's my dilemma though:

MFP puts my "resting" calories burned (i.e. the calories needed to maintain my current weight) at a little over 2,500 per day. I've put my settings to the most aggressive weight loss pace of "2 pounds per week", so it calculates that I need a 1,000 calories-per-day deficit, putting me at around 1,500 per day, which I am more or less hitting (with macros customized to put carbs at about 25%). Now, the "FitBit", perhaps because it calculates my calorie burn continuously, usually allocates an additional 1,200 calories against my "net". This may also be in part because living in New York is strenuous in itself- lots of fast walking, stairs, etc. throughout the day. Therefore, it ends up telling me that my caloric intake, accounting for a 1,000 calorie deficit, should be around 2,700 calories per day (meaning that I'm burning around 3,700.) That CANNOT be right, and seems to presume that I roughly have the metabolic rate of a cheetah.

Is it possible that the FitBit is massively overcounting the calories burned in my long walks, or that it is "double counting" calories burned via normal activity with the "resting calorie burn" already factored in? As it stands, my "Net Calories" as calculated by MFP/FitBit is usually either in the low hundreds or not uncommonly a negative number. I am hugely suspicious of logic that dictates that the only healthy way to lose weight is to consume close to 3,000 calories per day, particularly when all I'm doing is walking a lot.

I'm not sweating this TOO much, as I'm losing weight (though the beginning is always the easiest) and as I feel fine. I think that, for a man trying to drop body fat, eating up to 1,700 protein-heavy calories per day should not be unreasonable. But I wanted to put this out there in case I might be inadvertently doing a disservice to myself and to my longer-term weight loss goals.

Comments, advice and testimonial are heartily welcomed. A caveat: if you're going to bring up the much-mythologized "starvation mode" trope, please have some sound science to reinforce. A 1,500 calorie diet coupled with a few long strolls cannot be the definition of starvation, even for an American.

Cheers to all of you fighting the good fight.