You can add games and programs for Windows to the steam deck in Steam through the menu bar at the top (in desktop mode). In "Games" click "Add a Non-Steam Game to My Library..." and then select this exe. After it creates the game, you go into the properties for it and go to the compatibility tab. You should be able to set it to use the newest version of Proton (9 something) and after that it should load!
While you're still in the properties, you'll need to put this into launch options to get widescreen just for this specific game, haven't needed this otherwise:
-screen-width 1280 -screen-height 800
I have been adding random Windows programs and games this way and they work pretty well. Also lets you access it from the main steam deck menus and use the layouts which is nice.