Considering the Steam release is an entirely different game, and you have the itch.io version, you got the game you paid for.
It's unfortunate If you're in a situation where such little money causes so much issue, but even still I couldn't see being comfortable asking to revoke the financial support you've already given just so you can have what you want, especially considering now the itch.io version is going to be a collectors copy now that it's unavailable for purchase.
It's natural to feel disappointed because they originally promised that the Steam version would be available to those who purchased the itch.io version, but the game blew up in popularity and refunding everyone who purchased, or giving free steam keys, just isn't something we should expect from a Dev, especially if you actually enjoy their works and want them to make more games or projects in the future.
Your terrible situation of not having financial freedom isn't because of the dev, this is a low cost to have access to a new experience, you should be upset with your home situation, not the creatives you claim you wanted to support.