Hi,
I've never been a JW either, so I guess we're kind of in the same boat- except luckily my reason for being here (my girlfriend) has already left the organization. I can't speak as a witness then, but only as one who has had the privilege of being there as one soul winged her way free of the Tower.
Definitely take it slowly. It's the only way anyway, he won't respond to a frontal attack upon his belief structure, very few people can. You cannot throw all you know at him at once, his brain will almost certainly enter defensive mode and reject it all.
But... chances are good he will find out the truth about "the truth" one day. If you keep silent and don't say anything he may live a happy, contended, JW-life, but it is also almost certain that he will acquire doubts through some other means- so leaving him alone does not mean he will remain a happy JW.
My girlfriend describes the wonderful, peaceful feeling she had when she made the decision to disassociate herself. To live as a Witness, if you are at all aware of some of the problems and unloving doctrines (such as the one which threatens your friendship) is to live with doubts, with cognitive dissonance, and with self-reproach for having these doubts.
The Witnesses believe in a thing called "theocratic war strategies" which basically involve lying to people who don't deserve to know the truth. While this is a terrible ideal to preach, I think we all feel that it's an acceptable- or necessary- strategy at some times.
But in the end, I think the truth is a necessity, and I think the truth always produces the best results. This may be simply a naive, optimistic hope, but there you have it.
Your friend deserves to hear the truth- and perhaps that means from you.
It's the old philosophical debate: live a happy, contended life as a monkey, or a painful, difficult, wonderful life as a human. I think we all have moments when we'd like to be that monkey, but on the whole I come down firmly on the human side of things. Ignorance can be bliss, but living free and true is the wonderful fate of mankind.
I think you can live a perfectly contented, animal-like existence as a JW. I do not think you can truly live- you can only exist, bearing on until the end of the world, which is coming Very Soon (tm).
I would wish life for everyone, and not consign anyone to mere existence(1).
It's not you duty to help your friend. It's not your fault if you can't free him. Everyone must (and does) walk their own spiritual path in this world. Remember that, and remember to be true to yourself and to him, and things will work out.
Best of luck, and please keep us posted.
t.
(1) of the sorry-I-stole-your-line-you-know-who-you-are class