I like this as a concept and it seems well-constructed. (I haven't run the game yet, so can't comment on how balanced or imbalanced it may be.) I think it's smart of you to note that although the wendigo comes from Algonquin mythology (in North America), there's no reason the same types of spirits couldn't descend from the Arctic Circle to appear in Sami or other indigenous folklore. That said, you might want to establish a localized name for the creature. Perhaps the creatures have a name for themselves which has been translated into local languages, accounting for some similarity of the name used in the Mythic North. That way, you could just juggle some sounds around to make "wendigo" sound more Finnish.
I also appreciate that you included a means of defeating the creature that doesn't require combat. Media depictions of wendigo-inspired monsters usually make them purely physical threats, to be dealt with purely physically. But if the creature is no more than teeth and claws, you might as well be facing a rabid animal. Nice to see a bit more consideration in this version. Still, I'd like to see more complexity in their motivations or personality -- is there even room for a personality, given that they are driven by ravenous hunger alone? (If not, I think that's kind of a boring monster and I'd probably never use it. Again, it could just be a pack of starving animals.)
You mentioned that over time the wendigo becomes more feral or bestial and takes on more animalistic features. I like that detail a lot, and it suggests that a more newly-created wendigo could be less feral or animalistic. Maybe a newer wendigo retains (however briefly) a vestige of its human memory and personality. This could allow for more complex motivations for a wendigo antagonist.
As an example, maybe there's a brand new wendigo formed in the body of a hermit or outcast from the local village. Now reveling in its new power, the creature decides to take revenge on the town that treated the hermit so shabbily. First, it "converts" other folks who operate at the edge of the village -- a farmer, a herdsman, a woodsman -- and assembles them into a pack, with the intention of swarming and devouring the entire village in one bloody night. But first, the herdsman's wife writes a letter to the Society...