Why won't you upload this game on Steam? More people would know about this game, and more payment optins will be available (for example PaySafeCard, which I have).
The itch.io platform is easier to use (it takes less work to get a game project set up). Also, our old Shockwave games are not good enough quality wise to compete on Steam. There are quite some technical problems with the games that are hard to fix for a proper Steam release. I'm sorry that Itch.io doesn't have the payment options you want to use, but you're better off complaining to itch.io than here ;)