Yes, producers have always had the incentive to innovate, and yes, they have always tried to do so (even slave economies were "capitalist"). Only in certain institutional, cultural, and geographical contexts can they be successful. I also think base levels of scientific knowledge are critical (but Anton may disagree in some cases).
As for demand, I refer you to Mokyr's classic piece: http://www.jstor.org/stable/2119351.
So, sort of. Everything is endogenous. Desmet and Parente argue that market expansion leads to longer firm production runs in differentiated... (read more)
Historian's perspective: the Industrial Revolution was primarily a supply-side phenomenon. Demand may have helped to geographically focus the concentration of new sectors, but technological change occurred because of the desire of producers to make things better and at lower cost, not because idiot peasants realized that cotton clothes were comfortable. Other factors—science, bourgeois/Protestant ethic, coal/raw materials, skills—are also supply side.
Neither necessity nor desire is the mother of invention!
Ha, I wish. Maybe a children's illustrated encyclopedia.
Market expansion is definitely an interesting area for research here. Foreign trade shares in the economy were small, but in certain key sectors (i.e. textiles) it was pretty significant. But again, it's important to unravel whether these markets can be considered A) additional demand or B) won by higher-quality / lower-cost production. That's the story of the "New Draperies" in the 17th c. and cottons from the 18th.
Anton and I have chatted about this a lot, and I agree with most of this. ... (read more)