Keep up the good work.
A possible reference to include is to the ESP12e Devkit User Manual :- https://www.gitbook.com/book/smartarduino/user-manual-for-esp-12e-devkit/details
It is not comprehensive, but better than nothing.
Under the "Areas of Research" section, regarding the second item (about whether an entire library gets pulled in, or just the object files that are needed) - my understanding is that only the individual object files that are needed are pulled in.
Source: Static Libraries section in Beginner's Guide to Linkers
The entire article is very well written introduction to what exactly linking does, and you might enjoy it.
Not that the Wikipedia Arduino page jumps between calling the chips at the heart of the Arduino a microcontroller and microprocessor.
And thanks for putting this book together. I was waiting for something like it to come together before jumping on the ESP-8266.