Micro-drill pinholes: http://www.pinholeresource.com/shop/...category_id=16
All photographic paper has a ISO rating: http://www.ilfordphoto.com/Webfiles/...0200232336.pdf
The best way to determine how sensitive the paper is that you are using is through testing.
Paper flatness all depends on what YOU want as a result. In paint can pinhole cameras, the film or paper is curved along the wall of the can. In a traditional pinhole camera, the paper or film is held flat. If you want it wavy, try it out.