1) I didn't discuss medicine and health extensively because that one of the reasons we are collectively living longer and healthier lives. It is not necessarily one of the drivers of slowing population growth.

2) In the past yes. In the future no. Don't forget we are just learning how to be a global species. We have only been one for a few decades (at most 1-2 centuries). That is not very much time and it takes a great deal of technological innovation for a species like ours to create a sustainable and well-managed global energy economy (not to mention a lot of fighting against the established energy economy). But the future energy economy will not expand our ecological footprint. It will be based on solar (and then nuclear fusion). Both types of power are unlimited and produce no negative effects for the Earth. Here are three talks by Michio Kaku about the future of energy. One is near future, one is about the future of nuclear fusion - the other is deep future.

3. I'm not sure what you are talking about re: civil wars. But any major wars would definitely alter the progress we are currently making of slowing population growth. However, I am very confident that the trends of declining war over the past 60+ years will continue. Check out this post if you want to know more. Of course there will still be war (and America is still perpetually at war - for how long I don't know). But major nation-state wars do not happen anymore. Those are the biggest threat to continued slowing of population growth because they would destroy many people's standard of living. Civil wars (if they happened in the BRIC) would also be bad - but if they just happened in one country it wouldn't be catastrophic for the overall global trend.

4. The line between the western world and the developing world is really no longer existent. They are not mutually exclusive concepts. Many developed countries are now non-western (e.g., Japan, South Korea, Singapore, etc.). As we progress towards the 2020s, 2030s, and 2040s, many other non-western countries will reach developed status. Of course it will take a few decades for India and China to reach these levels because it takes that long to pull 1+ billion people out of poverty. As a result, the further we progress into this century the more our species will adopt a collective and community mindset towards the population problem. Many organizations are already taking it into their own hands to ensure that we collectively slow the rise of the global population. These organization are international, without allegiance to one culturally constructed area of the planet. The U.N., and the Bill and Melinda Gates Foundation are great examples of these organization that are doing phenomenal work to eliminate infant mortality, reduce the spread of communicable disease in the developing world, provide greater access to female education, and develop cheap and easily affordable contraception.

5) We will be vertical farming by 2050 (in response to the arable land issue). This will also like by a urbanized business (increasing the rate of urbanization as rural living becomes functionless). Global warming is a major threat but a transition to a solar economy will start to fix this problem. We must meet the global warming problem or else we will threaten our own existence - so we will meet the problem eventually. Crises spur major adaptation - punctuated equilibrium like change. That is one of the reasons I'm so confident that a major energy transformation is going to happen before 2050.

6) Finally I didn't even have a chance to talk about how ubiquitous global internet and A.I. would probably accelerate the process of global female education and increase the rate of urbanization. Also, both of these phenomena will also likely make us more democratic and more peaceful - enabling us to continue raising standard of living world wide without any major war to get in our way.