Hi Am,
I don't have much advice, but I will tell you that Jehovah's Witnesses are a very closed society. They are taught very deeply ingrained ideas about those on the "outside" in "the world" and relationships between believers and "unbelievers" are very difficult. Even friendships of a non-romantic nature are strongly discouraged and looked down on, so even if your bf is not just on the rebound and a real relationship develops between you, the two of you will have a hard time.
But I wish you both all the best, and who knows, you could be the one who helps him out of the high-control religion that he is in. Hopefully you will not join them. They are extremely judgmental and their love is very conditional and surface, and their shunning policies are very cruel, destroying the happiness of many a family.