Thanks for writing to us about the difficulties you are experiencing with your son. Children succeed the most when they feel secure in their environment. Security takes root when the rules, boundaries and consequences are consistent.
The change in your son's behavior may be a result of the variation between parenting expectations. Perhaps you and your wife have different expectations that encourage your son to act differently. This doesn't necessarily mean that your ways are wrong and her ways are right; it just means they could be different. This also doesn't mean that your son is manipulating because he may not even know he is doing it. As a solution to this problem, maybe you and your wife should go together to a karate class to see how your son responds.
One of two things will happen: He'll either do just fine and go ahead with class, or he'll become clingy towards you and start crying. If he does fine, then he'll know you saw what he is capable of doing, and you can hold him to this expectation every time. If he becomes clingy, perhaps his mother can intervene and help you and your son reach a positive experience.