You can't put free games on sale at all.
(But you're free to change your prices, remove them, and reinstate them.)
Hmm. I do not know how the game in question was priced before or during the sale. Now it is pay what you want. And no tier to get additional files.
There are several 100% sales of games with pwyw but they have a minimum tier to get additional content.
Unless the intended sell price on Steam is 1 $, op needs to set a minimum amount anyways. People could claim the game right now and later a Steam key for the minimum payable amount on itch.