The JW organization has programs in many cities, where elders will visit prisons to preach to prisoners. It's the perfect audience- captive, downtrodden, and with lots of time to reflect. It's no surprise if your ex has suddenly discovered religion, or that he is favoring the JWs.
As others have said, a doomsday cult isn't the best place for anyone, especially children. And their record in dealing with child molestation and sexual abuse is horrible. Personally, I think you're just fine being non-religious. It means you're a step ahead of the pack. :)