So you have less weight to lose than before?

And you have increased activity more?

Eating level has gone down?

With only 20 lbs to lose, you taking a reasonable 500 cal deficit at most?

You going for avg weekly TDEE method or using MFP method with exercise logging and eatback?

If doing TDEE method, besides figuring out exercise in there - did you account for fact with kids you started out at Lightly Active, exercise just added on top of that?

If MFP method, are you accurate on logging times of workouts, and base activity level is also Lightly-Active?
Weight lifting is just that in the database, but should not include cardio warmup/cooldown, just lifting and rests between.
Running is actually pretty accurate if you have the pace correct. For the C25K, average pace based on time and distance is close enough.

Sounds like the lifting is suffering if little progress, body may appreciate and let go of some stress-induced water weight if you get out of the diet for a bit - when was your last diet break?

Those calories burns don't sound unreasonable - sounds like using Fitbit with HRM, so calorie burn is based on that.
Daily living though is based on steps.
So accuracy of steps seen, and more importantly distance, is used to calculate daily moving time.

Non-moving time is given BMR level burn - so actually it underestimates on it's own.
Because when awake you burn more - RMR level burn.
When standing you burn more.
When eating you burn more, about 10% of calories eaten.
None of that is accounted for - you don't need to create extra deficit unless you just think your food logging is awful, done by measurements and guesses.

As female, 1 week isn't a valid data point, as your BMR literally changes through the month. So the fact you maintained seems to say your maintenance is higher than you think though - ate more and exercised less.

I think an accurate 1 lb weekly would be more reasonable with only 20 lbs to go - if you have good sleep habits and not many other stresses in life. Change to 500 deficit at 10 lbs left though.

Fitbit is estimating total daily burn - as such your BMR is indeed in there.

Rarely will you find a HRM, machine, database, ect, that gives you the estimated calorie burn of just the workout. (bikes with watt meters being the exception, or machines that convert from watts seen in their formula to calories).
Because frankly, is it above BMR - would you have been sleeping if not working out?
Or above RMR - because you would have been sitting otherwise?
Or above lightly active because you would have been playing with kids or pets or housework, ect?

Nope - BMR should be in there for something reporting the calorie burn during a block of time.

So Fitbit estimate is indeed that block of time - total burn, just as any other device/database would be reporting.

You can only compare the Runners World calc if the distance you used there is correct.
Fitbit could seem high, and indeed could be too high - if the HRM isn't accurate - at least it sounded like you had the HRM version. Now, good formula with true values (flat on inclines or wind), avg pace, ect - are more accurate than HRM.
http://www.myfitnesspal.com/topics/show/773451-is-my-hrm-giving-me-incorrect-calorie-burn

Do you use your activity record from Fitbit to tell you the distance to use in that other calculator?
If distance is wrong, then pace in the calc is wrong too, so would be calories.

Also look at purpose of calc - they could be saying here is the extra amount you could eat based on what you did - in which case that is correct way of doing it - leave some calories out. (275-38 = 237, close to 225).
But if they are doing it that way - that's a perspective of what have you done extra above and beyond (without actually knowing what you would have done otherwise).
But Fitbit is also being accurate for that block of time - and that count is accurate too.
But not if you were to lift that 275 burn figure out and plop it down on a daily burn already accounting for the day. It would need to replace whatever was in that block of time already.

And that's what a manually logged workout synced into Fitbit or added to Fitbit does - replaces the total burn for that block of time.

I would indeed stick with the program unless you find some glaring inaccuracy in Fitbit's logging.
Like if you find the HR during workouts is way higher than manual measurement.
The distance method isn't used during workouts - only HR for calorie burn.

Besides, what % of your time and calorie burn is the exercise?
Compared to % of time and burn doing the active family stuff?
That small amount difference during the exercise is nothing compared to your daily activity burn.
If stride length is off there by decent amount - there's some error to your daily burn.

Yeah, treadmills have to be calibrated for belt stretch and sensor losing it - so not always accurate.

MMR on a flat route would actually be more accurate.

Fitbit either at the moment can have an activity record started - or if you note the time and duration you can create one later.
That takes a snapshot of the stats for that block of time - calories, steps, distance, HR profile.

You should indeed do a known route of at least 1/2 mile at average daily moving pace - not grocery store shuffle and not exercise pace walking.
The Fitbit adjusts stride length for each step you take - based on amount of impact and your stride length figure.
But it's best if the stride length figure is in the middle of the range it must adjust for, not on one extreme or the other.
Then with MMR distance known, and steps from the Activity Record - you can calculate the stride length you should use for best daily calorie burn calculation.
miles x 5280 / steps taken = stride length in feet.inches (say 2.4)
Record the 2 feet.
Take the 0.inches (0.4) x 12 = decimal inches (4.8) to record.

So exercise pace may be off a tad, grocery store shuffle may be off a tad - but the vast majority of your day walking/moving not exercise will be best estimate.

I didn't mean the exercise isn't substantial, though for most it isn't - the difference in accuracy isn't - because it's not the difference between getting a calorie burn for exercise and not getting one.
It's the difference between getting perhaps a high one and a low one. If the accuracy is off by 50 calories as you mentioned above - that's minor to the daily burn. And minor to the amount of inaccuracy in your food labels.

But - if that 531 example was the Fitbit calorie adjustment - you are misunderstanding what that is.
It is NOT exercise you do. May include some of it.
It is merely the difference between what Fitbit saw for your movement that day - and what MFP thought you'd burn with no exercise and your selected activity level.
You could get a big adjustment with no exercise at all, but more active day.
You could get no adjustment with some exercise, but especially lazy rest the day.

Yep, just stick with it, let go of the stress caused by it - and take measurements to see changes there.
All sorts of good reasons for water weight changes in the body increasing because of exercise, but one bad one too related to stress. So hopefully you got the good ones.

That is strange to start the activity automatically, which is somewhat based on steps - but then not give a distance.

Do you manually log any workout records?
If those are entered without distance, it leaves it as such.

That's correct math on what was extra daily activity if it catches those walks as separate.