Perhaps, from your perspective, but orthopraxic faiths really don’t make sense to orthodoxic traditions. Speaking for myself, “getting it right” isn’t that important to me, nor is trying to convince others that my way is the only way.
Powers That Be is just a more neutral term for gods, spirits, what have you. As for how I know, short answer: I don’t.
To some extent, yes. Again, I can only relate what I’ve heard from others, but it does happen that sometimes a god (or goddess) shows up in someone’s life, uninvited, and says: “HELLO! I AM SO-AND-SO! I WANT YOU TO WORSHIP ME!” (The standard reaction to this sort of encounter is: “Wait. what?”)
Some would say Cinderella is “the Goddess” in a different form (which I doubt). In any case, Cinderella, to my knowledge, never had an organized cult dedicated to her, and I don’t recall hearing about any modern-day “Cinderellites”, whereas there are modern Pagans who are dedicated to Lilith. Pagans who see deities as archetypal forces tend to be less concerned with historical accuracy.
It all depends, some gods are more demanding than others, and some gods will demand more from one devotee than they will another. As for whether it would affect me if I stopped believing in them, I don’t think my life would change that much. Now, for someone who is in a deeper relationship with them, asking them to stop believing in the gods would be like asking them to stop believing in their siblings. As for the afterlife, Pagan traditions are are more concerned with the here-and-now than what comes after. Tell you what, I’ll let you know after I die.
I suppose if my gods did not exist (in some way) I would be an atheist as well…on second thought, there aren’t enough holidays.

Pagans of all sorts love any excuse to party!