Summer, WOW. He looks beautiful and he stacked so nicely for you!! (Honestly I have seen other puppies show terribly, and he looks like he was a perfect gentleman ESPECIALLY for his very first show. Lovely gait on him, too!) You say he wasn't stacked nice in one of the pictures? I thought he looked great, LOL. I wouldn't worry about the front legs in the stack, just get them as straight as possible but with larger breeds they're always going to be a little 'wild' when they're that age, because of those knobby growth plates. I swear I must have told Dakota to "fix it" a million times when we were working on stacking, but for some reason those front legs just kept on looking like I hadn't done a thing to straighten them out. It's just a puppy thing.
Congrats on doing so well, and good luck in future shows!