Good on you for pursuing this goal. Way too many small dogs are spoiled to the point of not having any boundaries and end up being little generals running the house. Dogs do NOT want to be in charge. They only do so because of a perceived weakness in leadership -- power vacuum, if you will. This is never in their best interest.
Little Joel seems to be a smart dog, so with patience, positivity and persistence I'm sure you will succeed, and EVERYONE will be happier for it, especially Joel!