itch.io

"game insists on using a screen size wider than my monitor"

That should not happen. The config.ini says 

RESOLUTION = desktop

So the game should start in the resolution that your windows desktop has. And that should fit your screen.

If you write no for Fullscreen, you can resize all you want. But this does not magically change the aspect ratio of the pre rendered graphics. If you have other than 16:9 you will have black bars on the side or above and below.

Since you have a non standard monitor, you might be interested in this little trick:

Install autohotkey and use this keybinding in a   script

!^+SPACE:: WinSet, Style, ^0xC00000, A

In most games (including this one)   that are resizeable and can be maximized with the title bar button, you can achieve borderless windowed fullscreen with this method. 

Start game, maximize, press (ctrl, shift, alt, space bar) to toggle the title bar.

(Obviously you can chose another keybinding or another tool to change that window properties)

What irked me in the game was the slight mouse pointer lag and the lacking date  display on the save slots.   The content of the game is fine. I did play with the dlc, though.