DPI Wizard

I've updated the FOV Notes to include a link to a working FOV changer, use this to avoid any confusion

Set Building and Edit sensitivity to 100% to keep them the same as hipfire.

I've added the option to adjust the coefficient for Jedi's Trick now.

The game needed an update, so check again now. Your 8x will be out of range though, due to limitations in the game.

You have done it right. There's a quite big difference in the FOV between the games, so the Handgun Iron Sight / Reflex in MW is about the same FOV as hipfire in Fortnite. Not much you can do about this though, but it might make the relation between hipfire and aims feel a bit weird in Fortnite.

Since there is a mismatch between horizontal and vertical FOV because of the stretching, it depends on which axis you want to preserve. If they feel too fast with MDH 100%, switch to MDV 177.7778% instead.

You have done it correctly, although you should technically use MDV 178% and not 177.7778% to match Relative Coefficient 1.78, but this will not make a discernible difference.
That is what you should put in the config file yes, and for scalar 0 you have to choose between the two options depending on what you prefer.

As said above, the calculator already does "everything" for you, you don't need to know anything about the complexities of the math, you only need to specify how you want the sensitivity to be converted.
While it could be possible to to make AI answer questions such as
"What sensitivity do I need to set in-game in RoboCop: Rogue City with FOV 116, resolution 2560x1440 and 800 DPI to match the 360 distance of in-game sensitivity 1.48 Apex Legends with FOV 110, 3440x1440 and 1000 DPI?"
it would be faster and more reliable to just select these options in the calculator.

It's the "Viewspeed - Vertical" option.

Set the FOV in Aimlabs to the same FOV as you ADS in siege, then match the 360 distance. This will make it identical.

Since Legacy MW is based on a specific FOV, you have to use this FOV as the source for your conversion. So do like this, and just change the game you are converting to.

The vertical FOV is the same with 4:3 stretched and 16:9, so you need to switch the conversion to MDH 100% instead of MDV 133%:
https://www.mouse-sensitivity.com/?share=1083d3cd8f5b3a3010a2dd484aba6bdd
That should feel better.

I do agree that this would be a good thing to have in place, I will try to get it up and also integrated as soon as I can.

The in-game sensitivity has a quite limited range, if you use the config file instead you should be able to match it without changing DPI.

The recoil, and any other forced movement like sway and head bob, are based on set parameters that move you x degrees up, down, left and right. It is completely detached from your sensitivity setting. If that is what you were asking  

This is not related to the discrepancy shown by the calculator. This discrepancy shows you what the sensitivity/360 distance is with the calculated sensitivity is compared to the target sensitivity/360 distance, and is caused by the lack of decimal support by the game.
The inaccurate slider note means that when you set the slider to say 3.3 it might in reality be anything from for example 3.21 to 3.39. This is the case for a lot of games unfortunately, and if there's no config file option there's not much you can do about it.
This will make the actual sensitivity differ from the calculation, but usually not by a significant amount. Although this will vary depending on your sensitivity. If your target sensitivity is for instance 0.2, and the actual sensitivity is 0.29 due to the slider being inaccurate, you will get a significant difference since it's 1.45 times higher.
 

My bad, I thought they had moved everything to the GameUserSettings.ini file. I've fixed and updated everything now

Since Fortnite is 3rd person and has a quite narrow FOV, it's really hard to make it "feel" the same as a 1st person game with a wider FOV.
What you have tried is the correct way to go about it, but I would suggest also trying 133 and 178%.

In that case you can just use the normal Black Ops III calculations, they are the same as the boii client but with the fovscale locked to 1.

Nothing is really necessary as it depends on you preference. The positive of matching everything to Windows using MDV 0% is that 1 pixel movement will always be the same. The downside is that this will drastically affect especially hipfire when your FOV is different. 360 distance is usually preferred for hipfire as it keeps a constant movement for orientation rather than aim. So you know how far to move your mouse to turn around a corner etc. With MDV 0% or a match made to Windows/Desktop, this distance will change depending on your FOV. And while it keeps the aim consistent, this is usually less important than navigation when it comes to hipfire.
But it all depends on the game and your preference, nothing is right or wrong, what is important is what feels natural to you.

It's unsupported because the sensitivity is directly affected by the framerate, making it very unstable and any sensible calculation impossible.
So as to your question of "when", it will be added when the devs fix this issue

Sensitivity 2 is the Coefficient (you can see this in the output), and the 0.68 is the scale for the ADS conversion, where also enter the coefficient so it matches, like this:
https://www.mouse-sensitivity.com/?share=f42f0a7af910c8457de15d13bdc1db5a

Trigonometry
https://www.wolframalpha.com/input?i=tan((PI*74)%2F360)*cot((PI*66.6)%2F360)

The relation between the actual FOV and the monitor distance is calculated, in this old video you can see it visualized:
 
This is Monitor Distance 100%, and depending in whether you use the horizontal or vertical FOV to do this, you get either MDH 100% or MDV 100%. The method will for many make the scopes feel too fast, since you need to match the movement to the edge of the monitor (side for MDH, top for MDV) to actually match the movement. Monitor Distance 0% however, will match the tracking speed, i.e. the rate at which you move your mouse to track a moving target.

Actually, do you have zoom enabled in Windows? 150%? It might affect certain games like Roblox. If this is the case, multiply the sensitivity by 1.5 to compensate for the zoom.