On my return visit to Calvin's I was pleasantly surprised to see that his foster mom had been doing her homework. She was walking Calvin every day, with some improvement, and playing structured games with him more at home to help get out his energy. On the second visit we focused again on the jumping and nipping.
When dealing with any dog, but especially a very large one, it is important to remember how you carry yourself, what your body language is, and what that is saying to your dog. Many times people become intimidated by their pet's unruly behavior, emotions like these will affect your training in a negative way. Remember to say calm, but firm. You are in charge, not your dog. The key is to find what motivates your dog to do the things you ask of him. For most dogs, and for Calvin, this is food.
Positive reinforcement training using treats is very fast and effective way of training your dog. We worked on an "Auto-Sit" with Calvin while coming up to him to say hi, and at the door. The more you can repeat these activities, the more chance your dog has to do the right thing and get rewarded for it, the more he will perform that behavior for you!