Your first point is simply wrong, the stats I posted are for open play crosses. whoscored.com shows crosses from open play, corners and free kicks in separate categories and the former cannot be comprised of the latter.
No, they don't. For example Total is at 1.2, crosses at 0.7, corners at 0.4, freekick 0.1 and others 0.4. The different types are superior to the total. Now go to the mach center and chalkboard pick young>passes>cross and you will spot the corners.