Help with accurately calculating calories burned?

I'm sure this topic has been done to death.
My food diary is open, and though I'm not especially familiar with the settings here despite having used the app for a while, that makes me think my exercise and other information probably is too.

I've stopped losing weight after a 40 pound loss (not a quick loss, started Dec 2017). I've tried a variety of things to continue the downward trend, and as best as I can tell, the tools I'm trusting to calculate my burned calories are probably wildly inaccurate, so my deficits are wildely over estimated.

I've got a fitbit Versa, went from distance walking to running in an effort of raise my HR thinking that would help. It HAS, and I'm seeing benefits, but not on the scale. So....... Follow me on this and check my logic?

My daily step goal is set at 10,000. With walking and runs, my daily average is around 12500.
Clearly those are going to be big differences between casual errand walking and for example the ten mile run I did Sunday. So, ignoring what Map My Run and my Fitbit are saying for calories burned, I'm thinking I should still attempt the daily step goal. For walking, just ignore the calorie adjustment and keep my intake around 1400. For running, use the equation of {Calories Burned = [(Age x 0.2017) + (Weight x 0.09036) + (Heart Rate x 0.6309) - 55.0969] x Time / 4.184} for running and adjust somewhat for that.

So....does that track?
It has been pointed out that my daily logging needs tightened up, so I'm aware of that.
Would it be reasonable to use the heart rate as recorded by the fitbit, or should I manually check my pulse at certain intervals?

Also, ARE there fairly accurate apps or other tools to use for calorie burn?

Yes, I know I'm overthinking things. It is my curse. Just trying to get enough information to be able to use it.