1) I just made the amount configurable. I had this feature implemented but disabled, because I didn't want people to stop to decide how much to ask for. One less thing to think about. That's how uploading to ptwi is 20-30 times quicker than Ks.
2) What would you suggest to improve this? Similar to (1) I didn't want people stopping to think about spam when creating the project. I had a version where the qrcode was in /prove and I didn't like the user flow. I also disliked it visually. I made three changes now that might help. Reduced the amount to $5 (I hope it's not too low), explained posting projects is anonymous and how it fights spam, and explained in /prove that making a project public will need to pay to prove the project isn't spam.
3) Maybe /project should include a link to a page that explains what cryptocurrency is and what money is. I'll add this.