Sharon, don't worry about feeding him too much. He is a pup so he needs well fed. Besides, chunky pups are the best! As for training classes, we started Ceilidh after her 5 weeks of puppy classes and half way through the training ones she got bored and hit the teenage "I won't do it" phase. Start him when you feel ready, so what if he isn't the best in the class to start with, he will progress so quickly that he will beat the rest of them come the end of the classes. He is just a young pup, so he will learn more quickly than an older one.

That is just my advice, see what everyone else has to say too.