Reddit mentions of Introducing Buddha: A Graphic Guide

Then I recommend this book

It's very basic and introductory. It goes over the early history and briefly discusses the three major divisions of Buddhism; how they developed historically and in relation to each other. It might not answer all the questions you're looking for but it's a good place to start.

Just skimmed some of your other questions and the classic mistake most westerners make is to assume that it's an "atheistic" religion in the sense that nothing supernatural happens in it. Sometimes you'll see it described as "nontheistic" to distunguish that their relationship to gods is a bit different from western religions, but things like spirit possession, supernatural powers, and god-like things exist to different degrees in different Buddhist schools. It is very much a religion, don't let anyone tell you it's "more like a philosophy".