1. In regards to a canorsaur's ultimate predator rule, are the D3 extra wounds inflict for every wound applied only to an individual model, or does it apply to the whole unit?
the carnosaur inflicts d3 wounds on a model per attack. In the case where unsaved wounds get multiplied all those wounds are inflicted on the same model. For example, carnasaur deals an unsaved wound to a clanrat with one of its attack. You roll d3 wounds for ultimate pred and get 2 wounds. Both those wounds are on THAT clanrat. Obviously, this makes it pointless for you to roll the d3 unless it's a challenge or the model has more than one wound left.
There is also a lovely little rule which allows multiwound causing hits to splash on multiwound targets. Example: You attack a group of ogre bulls, you do three wounds with the carn, this would remove a model, however since it splashes you multiply and do 5 wounds instead, killing one bull and damaging another. i found out about this rule at the last tourney i went to, if it is false, do let me know.
Warhammer rulebook pg 31, Shooting, Removing casualties, Multiple Wound Casualties, second paragraph.