im unable to issue refunds because itchio doesnt do that as far as i know (ive had issues with games on here and when i messaged they told me they cant do it as well so i just dealt with the loss)
you can try to contact your bank and ask for a charge back but thats the only thing i can think of
sorry you were unable to play the game, though i have heard if you run the game as administrator it helps with the fps issue on weaker computers so maybe you could try that first? O: