I also put N/A in 13, actually it was already typed in there for me. I had a prior security clearance, so I put that date in block 32, but if you aren't prior, you should just leave it blank. You should have already been granted at least a Secret clearance since that is one of the prereqs to receive an unconditional acceptance. If Mr. Kush really needs it, he can get the info from the security guys at USU.
Agree on leaving the "accepted on behalf" portion blank. Mr. Kush will take care of it and yes, send everything to him. As far as I know, he's the only guy that takes care of AF USU/HPSP students. Don't worry, as long as the paperwork gets to him, he will take care of everything and if he has questions, he'll call or email you.
Good luck!