Great work, Robert.
I performed a very similar, back of the napkin analysis on the same issue years ago (right after the 2002 USDA study came out), and came to very much the same conclusions (as you probably have been able to tell).

Simple mathematics, combined with published and documented research, leads us to this inescapible and quite honestly, common sense conclusion: Ethanol from corn as a replacement for gasoline is a joke. A cruel one, at that.  
This push for "E85, everywhere!"  is yet another smokescreen for a poorly though out plan to put tax dollars in the pockets of ADM and Cargill, sell more obsolete, heavy, and inefficient GM made vehicles, and raise food prices.  
Westtexas's 'Iron Triangle', of course, supports the notion completely. Anything to distract us, the unthinking populace, from the real and inconvienent problems at hand.