I actually think your proposed travel is legal. Here is the T&C's for blackout dates.
I have bolded the part I think pertinent. Your travel originates on Dec 25. The transfer that continues your travel is within the blackout period.
WHAT DO OTHERS THINK of the wording?
Personally I would PM the Amtrak insider and ask.
For the period from January 1, 2012 through December 31, 2013 travel origination on Redemption awards may not occur on the following dates/times: January 2, 2012; February 17, 2012; February 20, 2012; April 5–6, 2012; April 9, 2012; May 25, 2012; August 31, 2012; September 3, 2012; October 5, 2012; November 20–21, 2012; November 24–26, 2012; December 20–23, 2012; December 26–30, 2012; January 2, 2013; February 15, 2013; February 18, 2013; March 28–29, 2013; April 1, 2013; May 24, 2013; August 30, 2013, September 2, 2013; October 11, 2013; November 26–27, 2013; November 30, 2013; December 1, 2013; December 20–22, 2013 and December 28–29, 2013 and January 3–5, 2014.
if you cannot get what you originally wanted then Can you do it in reverse leaving lax on Dec 24 and Seattle to chi on the 25th
or leave Seattle on Dec 31 and transfer to the zephyr for chi on New years day?