This guide might be useful for you, it’s about how to make a single executable for Unity games: http://ludumdare.com/compo/2016/04/21/how-to-make-your-game-into-a-single-exe/. I followed this guide for my game! It’s not perfect, but works for most cases.
Using the itch.io app, I’m not able download/install this game, I had to do it on the website. Even after this jam, I figure a lot people will be turned off by not being able to install. Consider adding a single exe, or make a WebGL build