Hey glad you enjoy the game!
Yes, the demo will be free on all platforms! As an FYI when the game is on sale in bundles I do think it's possible to use paypal then, so consider buying at those times, or maybe get the game on steam when it comes out there.
As for help, at the moment we have write and someone to help with story planning but feedback is always appreciated. If there's things you'd like to see feel free to make a post and tell me!
Fan art is ofcourse allowed, I even have a tag for it, so if you make some post a thread here!