I appreciate your balance, and thanks for the good and kind words.
Regarding your question: “how much leaven will you tolerate in a loaf before you decide it is no longer acceptable?” I have this to say: Leaven is sin, and the cause JWs stand for is something like a precious metal diamond over which leaven has no effect. That cause is this: Man has ruined (not ruled) his inner world, outer world and system of things which calls for a reaction from the God Almighty.
In this core belief, they have not erred, and will not err. If at all they have erred, it’s all in supplementary teachings which are too insignificant to shake the very core teaching.