It looks to me like your arguments A and B contradict each other. First you say that God is a hypothesis that is supposed to account for certain phenomena. Then you say the existence of God is not falsifiable. If it’s not falsifiable, then it can’t be a hypothesis designed to explain something.

I agree that Russell’s argument is flawed but for different reasons. Here’s my take on it.

The Tilde Fallacy and Reincarnation: Variations on a "Skeptical" Argument.