Cognac,
Be calm and take it one step at a time ,softly ,softly catchy monkey.
When the time comes tell him that you no longer want the Jehovahs Witnesses' as your religious advisors and when he asks why , tell him that you have gained a far better understanding and insight into their errors and malpractice than you could have dreamt possible. Also you can tell him without getting into an argument that he could find it for himself as the information is out there if he cares to research it.
Best Wishes.