How much further can you pull back?

[Polymirize]

Up until a couple centuries ago, this idea that he was a non-real being somehow not in our "plane of reality" was completely foreign. God was a literal man living above the firmament of the sky.

Wow. there's an obviously false blanket statement.

Look, there probably are some people whose beliefs are just as literal as you always take them to be. And those people are obviously less developed in the use of human reason, though it does seem to make you feel like a big man when you point that out...

For the most part though, there seem to be vast numbers of believers who in recognizing that god is outside of human comprehension, actually end up believing some cool things and functioning amazingly well for society.

There will always be something we don't know, something more to learn. There will always be something happening outside of that narrow spectrum of existence that you recognise as reality.