You are right- in most states if a shelter even thinks the dog may have wolf in him-whether by hearing someone say it or the dog resembling one-they have the right to euthanize.
In most states a wolf-mix dog has no rights at all.
I'm not sure where she got the info on him being 25 malamute/75wolf -this may have been a guess from her knowledge and experience with wolf-hybrids, I know Timber's eyes were amber-which is common in large content hybrids. ( I saw pics of him) In a low content they would have been brown like most malamutes.
As for exact percentages-there is no way to tell really-these are guesses and estimates. Unless you had the wolf-the dog-and the resulting babys and then mixed them-etc. But there is no real way to tell - people put the percentages on the animal to make it sell better.
The whole wolf-hybrid industry is a mess- you think the pure-bred dog industry is bad!