http://mc2.cchem.berkeley.edu/Smells/That is for your second question.
the gas products were 27–40.96% (wt%)
...
The gas products were analyzed by gas chromatography (GC) as CO2, CO, H2, CH4, C2H4, C3H6, C3H8, etc.
Long URL This all makes sense, as corn is most likely composed of mostly cellulose.
So I am not sure what you smelled. It might not have anything to do with the decomposition of the corn cob and the chemicals produced, but with the bacteria responsible for it, or critters munchin' down on it. There also might have been some trace amounts of alcohols produced, depending on what exactly was causing the decomposition, and that might have been what you smelled.
This was hardly a scientific "experiment"
and as such no empirical definitive conclusions can really be made.
Plus, I know so little about corn and bananas beside that they taste good, to come up with anything better! Anybody else?