900GB? That doesn't sound remotely right, the entire unzipped folder is no more than 3GB. I have no idea how it would possibly ask for 900, I don't know if there's much I can do to help you there. As for the Steam question, I currently prefer leaving it on Itch as I'm unfamiliar with the process for Steam. If I continue working on the game and it eventually gets to a more robust state I can be happy with, I might move it to Steam. For now I prefer the casualness and freedom of Itch.