Book on the history of Darwin's discoveries and development of his theory
I'm not certain it fills every element of your question, but I really enjoyed Michael Ruse's "The Darwinian Revolution: Science Red in Tooth and Claw."

It's especially good for setting up the collection of worldviews that predated Darwin, and the influence on him by both biologists/anatomists as well as very crucially geologists like Charles Lyell (Darwin really thought of himself more as a geologist; the long time prior to publishing Origin was largely because he was trying to build up some scientific chops as a biologist).

The aspect it is most likely to lack is references to original source material from Darwin. While it certainly draws on such writings, I don't recall it actually containing reproductions of those writings, at least not on a substantial basis.

Importantly, however, this book is not a biography - it is a history of the scientific community at the time, centered around Darwin and Origin and placing them in relevant context.