I think you're right about the crate size, SVTNupe.
About play-biting: I read in a dog training book that if your dog play-bites, you should walk away from him, or turn your back on him. He will learn that his play-bites end his interaction with you. Saying "No!" or spanking the dog does not usually work, according to the book I read.
Dogs really need their owner to be the dominant figure. If your dog is play-biting you, it may be confused as to whether it is the dominant figure, and it is testing to see who is the "top dog". You may need to retrain your dog to establish the proper dominance/submission relationship with him. Dogs are usually unhappy if they are unsure who is the dominant figure.
