I like what you put together there- it's a fascinating look at a big chunk of time.  I think you greatly oversimplify comments about the 1970's such as "normal seasonal rallies that made sense to producers".  NOTHING in that time period made sense to corn/wheat/soy producers in relation to what they had experienced before.  Corn exports in the five years before the Russian Grain Robbery averaged 619 million bushels, in the five years following they averaged 1.397 billion.  In the early stages of that, there was nothing in place like the USDA export reporting that we take for granted now.  There was inflation at dizzying rates, a very different Farm Program structure, and the odd export embargo thrown in for good measure.

A closer comparison of 1974 to modern times would probably be if the demand base slowly built by ethanol and other domestic consumption had magically gone from 8 billion to 11 billion in 2010, export sales doubled in 2011, and then the drought of 2012 sent corn prices into the $13-15 area.   

I guess there's some of those outlying factors in the modern era, too- the global economic meltdown of 2008-9, absurd debt levels in multiple governments, ethanol mandates and associated political games, etc.