Interesting take, Lloyd.  First, it made me laugh, because MY
wife says I have an evil twin that shows up from time to time!  :)

Let me throw out one more "problem" and a suggestion. 

Problem:  If the curse on the
serpent was really a curse on Adam’s rebellious side, then why did his
compliant side also get cursed?

Suggestion:  If we assume that this story originated with Moses, and
was told or written originally to Israelites recently exodused from
Egypt, then we might look there for a key to interpretation.

The following is taken from the Wikipedia entry for Apep:

"In Egyptian mythology, Apep was an evil demon, the deification of darkness and chaos, and thus opponent of light and Ma’at (order/truth), whose existence was believed about from the Middle Kingdom onwards…

Apep was viewed as the greatest enemy of Ra, and thus was given the title Enemy of Ra…

As the personification of all that was evil, Apep was seen as a giant snake, crocodile, serpent, or in later years, in a few cases, as a dragon, leading to titles such as Serpent from the Nile, and Evil lizard. Indeed, his name is thought to translate roughly as Great snake…

In his battles, Apep…had assistance from other demons, named Sebau and Nak. Ra was assisted by a number of defenders who travelled with him, the most powerful being Set…."

And from the Wikipedia entry for Set:

"As he was the god of the desert, Set was associated with sandstorms, and desert caravans.
Due to the extreme hostility of the desert environment, Set was viewed
as immensely powerful, and was regarded consequently as the chief god…

The word for desert, in Egyptian was dshrt, which is very similar to the word for red, dshr (in fact, it has the appearance of a feminine form of the word for red). Consequently, Set became associated with things that were red, including people with ginger hair, which is not an attribute that Egyptians generally had, and so he became considered to also be a god of foreigners."

I
am no expert in these matters.  Draw your own conclusions. 
But I find it compelling that the Egyptian embodiment of evil was a
snake, and their great God’s main protagonist against the snake was
named Set(h).  I find it compelling that the Israelites, after 400
years of Egyptian enculturation, grumbling against Yahweh in the
desert, might turn to Set worship.

It seems Plausible that Moses
was incorporating Egyptian symbols in order to put all of these deities
under the power and plan of their own all-powerful God who, by the way,
created the sun (Ra) and moon (Thoth), which puts him in a whole
different league over Egypt’s deities.  This plan included making
a home for themselves in Canaan, not Egypt.  God creates a perfect
habitat for Adam and Eve through the parting of waters.  He
creates a cleansed habitat for Noah through the receding of
waters.  And God is creating a habitat for His people through the
parting of the Red Sea.  There are more parallels, but this is
enough to state my angle.