Just a quick question on correct terminology: is an animal detecting and moving away from a smell that either indicates danger, or else is simply extremely unpleasant, properly termed chemotaxis? Or is the term strictly applied only at the (unconscious) cellular level?

Chemotaxis typically refers to a hard-wired response of sorts. It can be based on chemical pathways within a cell, but can also be a multicellular system that forms a circuit that reacts autonomously to chemical input. It is not usually used in contexts of e.g. learned avoidance. 

Thus it can be applied to multicellular organism but usually only in the context of  hard-wired responses.