If he really is so confident about the Witnesses being right after reading all that apostate stuff then why does he feel the need to blow off steam at you? Why is he not just happy being himself and who he is and what he believes in?
What I can see is someone who is perhaps quite intelligent, but also insecure and scared and frankly lashing out in the wrong direction.
In some ways I can see myself in fact, because that is how I must have sounded a few years ago!
My advice in dealing with him would be not to engage in lengthy arguments about details. Commend him for his tremendous courage to read apostate literature when the society tries to discourage it through fear. That really does take some guts, and many of us have been there - surreptitiously reading apostate sites; borrowing apostate books from the library; hiding them hoping no one "finds out"; wondering if we are "evil" in Jehovah's eyes just for reading another point of view.
In going against the society's rules and reading apostate literature he has already made the most significant break from Witness ideology. Whether he chooses to go the extra mile down the road to explore other options is really a choice only he can make in the long run, and trying to push him when he is not ready is not likely to help.
Slim