1- Sure, it shouldn't be that hard to change the code to check against a different list of returns.
Right now the check function divides the wheel's rotation by 15 and decides to return the co-responding number from a list.
2- Yes, the design can be anything.
3- Yes, you just need some basic knowledge about renpy's screens. And if you're stuck, you can contact me on discord: kiaazad and I'll try to help you.