You need Reshade and Hex Edit and Steamless Unpack (for Steam games) for this. Crack version also needs Steamless Unpack.

Reshade:
https://reshade.me/

Hex Edit:
Offline
https://mh-nexus.de/en/hxd/
Online
https://hexed.it/

Steamless Unpack
https://github.com/atom0s/Steamless

Installation Instructions:

Install Reshade (Direct3D 10/11/12) with the two default options:

Standard Effects
SweetFX by CeeJay
Quint by MartyMcfly
Color Effects by prod80
OtisFX
Fubax (Aspect Ratio)
Legacy Standard Effects (all the way at the bottom).

You can add more if you want, but it might double some of the textures due to using Legacy Standard Effects. So these three alongside the first two default should give you enough customization options.

Check all boxes. Especially AspectRatio on Legacy Standard at the end.

Open the game. Open Reshade options (Home). Click Active on Top to arrange the options alphabetically. You can change the Reshade key in the settings as well as set location of screenshot key and screenshots you made. I just make the key F9 for Open and F10 for toggle on/off effects then screenshots is on its own folder within the game location (like Manager Files Folder >>>Screenshots Folder)

Make sure AspectRatio.fx is checked, then at bottom of Reshade window there's option sliders find the AspectRatio.fx and set the slide of "Correct proportions" to 0.344 for 21:9 -- For 32:9 keep moving the slider until it reaches the edge of the screen. I added a screenshot to make it easier.

To check it, save a screenshot via Reshade and open it on a picture viewer (I recommend Irfanview). Check the sides if it still has black bars. So just adjust until it's gone.

Close game. Now it's time to unpack your game. Locate your steam installed file "FATAL_FRAME_MOBW.exe"

Once you installed Steamless Unpack. Locate the game file and just unpack it. It will automatically create a file "FATAL_FRAME_MOBW.exe.unpacked.exe"

That is now that unpack file. Back up the vanilla version and rename "FATAL_FRAME_MOBW Vanilla.exe.unpacked.exe" to "FATAL_FRAME_MOBW.exe"

Then use this file for Hex Editing. Choose which version you prefer (Offline/Online). I personally use the Offline since it's quick and easy and has shortcuts

Press Ctrl + R or Replace All and make sure you are in the Hex-Values Tab.

Search For 39 8E E3 3F, select Search Direction All and Replace All with one of the following according to your resolution:

Here are the values for Ultrawide:

2560x1080 = 26 B4 17 40

3440x1440 = 8E E3 18 40

3840x1440 = AB AA 2A 40

3840x1600 = 9A 99 19 40

3840x1620 = 26 B4 17 40

5120x1440 = 39 8E 63 40

5120x2160 = 26 B4 17 40

6880x2880 = 8E E3 18 40

So if I want 3440x1440 resolution. I would replace 

39 8E E3 3F

to

8E E3 18 40

It will say "Replaced 5 occurrences of 39 8E E3 3F" That means you did it correctly.

Now for the Film grain removal. Stay on the file. Ctrl R or Replace All 

76 4E 6F 69

to

00 00 00 00

It will say "Replaced 7 occurrences of 76 4E 6F 69"

Your done. You can now play the game in Ultrawide. I added my own Preset with the Aspect Ratio fix already in.

BEWARE that you will have to do this EVERY SINGLE TIME the game updates (It will replace the .exe to Vanilla). This is the same way for Fatal Frame Mask of the Lunar Eclipse (I have to do all of this all over again each update).

So make sure to always backup Vanilla exe whenever there's a new update.