Will we overcome unsustainability and economic collapse. Global warming can not be properly reversed if we do not employ robotic means to exponentiate solar energy collection and electrical storage.

Question One:
That's the correct definition, however, all three could be true. Complete automation of solar energy collection and energy storage is mandatory! As for crude oil, humanity has already consumed an amount the size of a football field, 20,000 miles long (about 40 cubic miles)!

Question Two:
The EIA says:
Total U.S. coal consumption was 1,121.7 million short tons (in 08).
1.1217 billion tons divided by 100 tons = 11,217,000 railroad car loads was consumed. If each is 75 feet, then that train of coal would have to be 159,000 miles long.

Question 3: We need a cheap and reliable energy storage system (demand battery research!)
Sunlight = 1,000 watts at best per square meter (10.75 sq ft).
~ 800 watts for 6 hours x 15% (~ efficiency of collection media)
= .72 kWh x 1,000,000 = 720,000 kWh per kilometer x 100,000 km = 72 billion kWh per day or 18 trillion kWh per year (with 110 cloudy days).
World electrical net is 18 trillion kWh per year.
This is about 40,000 sq mi and is a little less than the area used for roads in the USA alone!

10,000 square miles of sunshine can power all of the USA (assuming just 20% efficiency). World deserts total to about 15,000,000 sq km or about 5.8 million sq mi.

Solar thermal using mirrors and molten salt as heat storage is about 20% efficient, and the Solar dish is about 31% efficient!

Therefore, it is safe to say that solar energy can support 20 full blown present day populations...