As to 1) the Tree Devil is taking a visible action, so Iīd say yes, the Totem may use its Wait action to strike.
As to 2), if itīs my own model, I would probably say they lose their shield bonus and Def modifier if they are caught unawares. If they let someone sneak up on them, they deserve what they get. If itīs my opponentīs model Iīd let him decide.
As to 3), Berserk vs. Fear is handled in this post:
http://forum54.oli.us/index.php/topic,597.0.html. I found the discussion very interesting as it is one of the unclear points in the game...
As to 4), AFAIK throwing spears when Charging is not counted as a missile attack but as an extra attack when charging, similar to the Dark Tusksī Tusk attack.