One thing that I would strongly urge is that you have to STOP telling him that he's not a JW until he gets baptized, because right now that will only make him want to get baptized ASAP.
OMG, that just gave me chills..... They are 'encouraging' kids to get baptized younger and younger now. Age 8 or 9 is absolutely within the realm of possibility.
I agree that you need to get him OUT.... Keep him AWAY from the meetings!!!! The more he hears the rhetoric, the more likely he will be to believe it. Even if he doesn't become a JW, then you run the risk of his going through life with a guilty conscience, thinking that he is not living up to what God wants him to do. Get him away from there....NOW!
I also think that you should open his mind to other religions, other books written for children. Take him to church. Read to him. Talk about the bible, about evolution, whatever you want! Open his mind, and then he will truly be equipped to make his own decision when he is old enough.
Wishing you and him all the best!
GGG