Don't worry....He won't need any therapy.
At age 16, going through all that those years entail, my wife also tried that crap with our son thinking that if she shoved WT material down his throat by making him read books an answer questions to her satisfaction that he'd do better. It was making them both miserable.
All it did was drive him further away. It was only my stepping in and putting a stop to it and forcing her to recognize that he wasn't interested in being a witnessand that that wasn't necessarily a bad thing that they have a relationship at all right now.
While the dynamics of your situation differ in that he's a "stepson", I'd probably suggest that you ensure that you're available as a sounding board for his frustrations as there will be many to come.