I just did what I should have done two days ago - I called the Massachusetts State Fire Marshall, Office of Code Compliance.
There are NO fire retardancy requirements for foam used in private residential applications in Massachusetts. None.
The VITA/Crest Foam guy was using scary words like "go up like a blow torch" and "liability" - evidently, he was covering their respective butts because EZ-Dri does not currently meet California Fire Code 117 requirements "for open flame and cigarette resistant materials used in residential upholstered furniture construction."
Moral of the story: don't panic; learn the facts. Now, if only I could remember this...