Before you can expect him to focus on you with distrations he has to have focusing on you without distractions mastered for at least 30 seconds! Be consistent and work with him a couple times a day! Make the reward something he can't pass up. Perhaps a piece of lunch meat or cheese or whatever really does motivate him since he is not dog food motivated. When you can drop the reward and he will maintain eye contact you know you are making progress. Then you can start working on the same behavior with distractions.

As for taking him down a different isle when he does get rambuncous, I would try a different tactic. Step on his leash at the collar and force him into a down. When he stops acting out then let up on the leash and release him. This position is called puppy management. He may struggle against you at first when you do this so do it at home when the distractions are not great. Then when you need to do it at class he will already be introduced and it will go a lot easier. Now if I step on Dusty's leash he automatically goes into a down.