Chances are if renewing at another port due to cost rather than avoidance of a particular CBP Officer, I would anticipate you would probably not encounter the same inspector. Therefore you may very well be approved with your initial package.
I would say if you are driving to another port as opposed to flying through the same airport where you encountered that particular officer, chances are you will get another inspector who might not be as fussy as your first encounter.
Revising the starting date is not dangerous but you want to ensure you are still in status while you are revising the next status, i.e. don't let your existing status expire while in the U.S. and have no new
TN lined up.
You would not present a letter dated like: "10 May 2009 to 14 may 2010" That might get you refused entry.
If you are starting May 10, 2009, then for a one year TN your end date would be May 9, 2010.