Milo and corn use about the same amount of N per bu, milo is a little lower, but its easier to figure the same.

Cant help with that question, but Id think you might want to shred it before or think about baling it. It leaves about the same amount of residue as corn will 

IMHO, the row crop head works better than the flex head with an air reel, but others will disagree Im sure. 

The biggest issue I think youll have is with timing, Usually we have to wait for a frost to before we can hit milo hard, trying to separate green stems and leaves from the grain is a PIA and youll lose a fair amount out the back.  You can dessicate milo using Rup or Sodium, to get the plant to die, but idk how that works for food grade, and Ive never done it before, I just know it can be done.