THIS WILL TEMPORARILY FIX THE PROBLEM, THE FOV WILL RESET AFTER ANY CUTSCENE.

1. Navigate to the configuration file(s) location:

(edit) Windows: C:\Users\Tai\AppData\Local\HighMoon\Saved\Config\WindowsNoEditor
Steam Play (Linux): <Steam-folder>/steamapps/compatdata/1065310/pfx/

2. Open Engine.ini.
3. Add the following at the end of the file and set it to read-only:

[/script/engine.localplayer]
AspectRatioAxisConstraint=AspectRatio_MaintainYFOV

https://www.pcgamingwiki.com/wiki/Evil_West#Game_data

First let's attend to the elephant in the room,
Can you use Cheat Engine on Steam games?
Here are some helpful replays to that question:

1. Generally don’t use it in any online multiplayer game or you will likely get banned from either the server or the entire game. (https://www.quora.com/Can-you-use-Cheat-Engine-on-Steam-games)
2. Yes you can use cheat engine on steam games, but a good rule of thumb is that you should not use it on any online multiplayer game.
3. Of course. You’ll probably get banned though. All online games made by Valve and even some that aren’t use Valve Anti Cheat (VAC). This system automatically detects modified game files, and administers a delayed ban that can take anywhere from a few days or a few months to take effect.

From my understanding you SHOULD NOT use it with online games. Close the program when playing anything other than Offline games. With that said, make your own research and decide for yourself if it's something you want to do.

Here are the steps for changing the FOV using Cheat Engine:
(Originally posted by Skely7426)

1. Download Cheat Engine. Windows may flag it as potentially unwanted since it's a "cheating software," but you can bypass the warnings safely.
2. Download the cheat table (HighMoon-Win64-Shipping_v1.0.CT) by Akira from: https://fearlessrevolution.com/viewtopic.php?f=4&t=22089
3. Open the cheat table (HighMoon-Win64-Shipping_v1.0.CT) by double clicking on "HighMoon-Win64-Shipping_v1.0.CT"
4. Open Evil West and stay in the menu
5. Alt+Tab to Cheat Engine
6. In the Cheat Engine window, click on the computer with the magnifying glass in the top left. Select the process "HighMoon-Win64-Shipping.exe." Select yes on the prompt to keep lists
7. Check the box to the left of "[Character]"
8. In the drop down, check the "FoV Modifier" and "Field of View" boxes
9. Set FOV to 100 (or more, it's up to you)
10. Alt+Tab back to the game and continue playing as normal

Don't exit Cheat Engine until you done playing, I think it may revert the FOV to default (comment if not)

Hopefully we will be getting a true fix from the developers.
Until then,
Happy slaying :D