If your son continues to be bossy, remove him from the situation immediately. If he throws a fit, completely ignore it. Once he has calmed down, tell him the appropriate way that he needs to behave. When you discipline your son, the main goal is to teach him rather than to punish him. When he is disrespectful to the way he responds to you and your husband, stop him dead in his tracks. He needs to be told constantly that you are not going to accept that type of behavior.
It seems as though he has picked up this behavior from somewhere else. He may have been influenced by older children or even a television show. He is too young to be acting in such a manner. You have many more years to go in dealing with behavior issues so you must get control of the behavior now.
You are correct in that you need to place more emphasis on the positive behavior. He may be acting inappropriately just to get attention. Try to ignore the bad behavior unless he is hurting others. REALLY put more emphasis on anything that he does correct.
What is an example of how I can "stop him dead in his tracks"?