1) In Choose Your Enemies Carefully: Secrets of Power Volume 2 the wendigo says he follows the Blight totem. In MITS however, it just talks about the followers of idol, animal, etc... totems turning to the toxic path. Does anyone have any rules, canon or otherwise, for playing a character who actually follows the toxic path?
2) Do you think it would be possible for a character to play a Toxic Shaman(Avenger or Polluter) in a non Toxic Campaign? I think that as long as the character played up the sociopath aspect instead of the pshcyopath parts and kept their toxic nature either secret or only revelaed it to those who don't care it could be played.

A similar argument broke out over serial killers and pedophiles as PCs.

You can, but the character might as well take the "limited time" flaw. And the player had best be understanding when (s)he gets smeared all over the wall.

-Siege

Blight could be another name for a known, twisted path. did the wendigo have any particular causes it espoused, beyond "kill all hoo-man"?

Considering the source, I'd say the Wendigo was a Toxic Druid of some nature totem.