I agree with others good suggestions here and handle this like - right now. Or as soon as possible. Your wife IS disrespecting you because she feels you aren't being the alleged " spiritual head " of the family - so she disrespectfully gets some other guy in the congregation to study with your son. That's ridiculous. First off I think you need to explain to your wife that SHE is in the wrong not respecting you by keeping you out of the loop. Then go tell the " brother " studying with your child that you don't respect him for going behind your back- then go to the elders telling them that you and your wife will handle any " teaching " of info to your son.
Bottom line like Outlaw said and you need to keep this firmly in your mind - these people ARE trying to break your family up. You've been conditioned by WT mind control to think it's to " help " or " assist " your son- the only thing it's going to assist is implanting thoughts into your son's head that YOU his dad are evil and his MOM is considered " righteous " by WT standards- so you lose by default. They try to cut you off from your son. It's time to cowboy up and take the reins on this horse and seize control of the situation or they will kick you off of the horse. Kind of how I see it. Good luck, we are here for you, Peace out, Mr. Flipper