I think there may be an Establishment Cause issue here. It is hard for a civil court to judge the relative merits of a set of religious beliefs. It would seem that even if the beliefs were harmful (like if someone was a member of the Nazi Party or the KKK), the right to believe and practice such things cannot be punished under law UNLESS there are some discernible damages to an innocent third party due to those beliefs. (Example: If the KKK commits a hate crime against a minority person due to its beliefs in white supremacy, the person (or survivors) have a claim against the KKK.)
Class action suits are even harder because a court has to certify the class under the state (or federal) rules of civil procedure. There is a test about the number of plaintiffs, type and similarity of claim, adequacy of representation and the like.
I think that you should spend your time investing in a public education campaign like this one. It is far more effective and less costly. Besides, the WTBTS is not going to fall down with one great blow. It is fading in its power to persuade and remain credible as a belief system (even to its own adherents). I am so sorry about the personal damage that has been caused to you and your family. Just tell your story to as many people in as many ways as you can. Remember that every day you know the "truth" about the WTBTS you are winning.