Yes, what arastangrider said is correct (if I understood it correctly). I would put him in a round pen and work on the join-up. There is another thread in the Natural Horsemanship section that is called "flip that horse". I really like the way that the woman in the videos did all her groundwork. I really think this would work for your stang. After you get him where you can touch him, I would not punish the nipping or the pawing with a pop on the shoulder yet. He is still deciding whether or not to trust you and that could break what little trust he has. I would make him move away any time that he did the inappropriate behavior and pressure him into circles until he stopped again. I would love to see some pix and I wish you luck. Mustangs are very smart and can be a real challenge. My 2 that I have are really sweet but I have to stay 1 step ahead of them at all times.
Here is a link to that other thread Flip That Horse!