You’ve done about all that can be done, short of contacting the EPA, and complaints are often a long shot anyway.
There’s a lot of politics behind car problems unfortunately.
Question though. Was this vehicle purchased brand new (as in 4 or 5 miles on it) or was it a dealer demo? (100 miles give or take)
Sometimes an improper break-in period can cause harm to the engine. While this would not be a problem on a new car, on a demo it could because sometimes a demo in the hands of the wrong person may get a real thrashing.