Well first, he's too young for a prong collar. You're doing more damage that anything. Second, is the hula hoop a toy reward?! I'd suggest switching to food rewards with a smaller toy reward like a kong wubba or ball on a rope....
Everything at this age should be positive and fun to build your relationship, not hinder it. Keep training sessions to 10-15 minutes, maybe even up to 20 minutes but ALWAYS end on a positive note so you don't cause stress and your puppy to not want to work with you.
The more people I meet and talk to,the more I love my dogs and their intelligence.
Shasta GSD 5/5/10 CGC
"Dax" Thor z vom Weberhaus 3/18/2013
Zena GSD 6/1/03
Riley GSD/BC 1/10/05-2/1/2013