When the following address:
is placed into this equation
in the //WA eCart Redirect Check Out" area on the "Checkout" page, the "Proceed to Checkout" action of the "CustomerInfo" page results in an immediate transfer to this PayPal website. The "Checkout" page is bypassed altogether. That is, it's bypassed as a visible/actionable page to the person involved in the transaction.
So, I've left that "entry" out so as to troubleshoot the field population issue - but, for you wondrous Sherlock Holmsian folks out there, it might be a clue!