I hate to be the killjoy but I will! You are going about this all wrong...yes it is true. Your training sessions are too long, do very short sessions and end on a positive command. If he starts to get too excited and not listening, he has had enough. His attention span is short, very short.
Don't give him too many commands until he masters one. From a sit, bring the treat close to his nose with the treat secured in your hand where he can smell it but not get it (another common mistake) bring the treat close to his nose and down to the floor. Be PATIENT! Re-work it, don't say a word!!!!!!!!!!!! Only say DOWN when he actually goes down and do not reward him right away. After a moment then reward him, do NOT release him from the down with food in his mouth and do not ask for a sit up right now until he masters the down and you have released him from it.
I like using a fresh energy laden puppy, I use the energy for training. If your goal is too wear him out, then you have the wrong idea. He is a puppy, training will stimulate his mind and tire him for a short time. Taking him to puppy socialization classes is what you want to do.
Don't do a stay yet at this point, when it is time I will walk you through the steps. Too many people do it wrong and yes puppy classes are a good option to enroll in. Find a trainer who does positive training, does not get frustrated, understands puppies and I really wish I could help you train.