For the Dusty Sachet, this is open to GM interpretation. I think I'd rule that it has a slower progression than normal pollen lycanthropy, that way the player doesn't finish turning into flowers between investigation 2 and investigation 3. But the disease will finish its course unless cured---whether by drinking the sachet's tea or by some other means.
Dismiss Into Figment is a little weird, since it affects Toughness. You ignore the Toughness part when it's used on NPCs and monsters, since they don't have Toughness, but otherwise it functions the same way. That said, it only affects a piece of a target. You would need to rapidly and successfully cast a lot of it in succession to whittle away at a god. With enough casters and hit points and a chained down god, you could do meaningful harm to it, but you would need a significant population dedicated to the task.
The Briefly Turn On You DR 16 that Haints created with Leash The Departing Soul have is the difficulty for them to attempt to hurt you. So on a 17+ they can throw an object at you or try to terrify you. The GM rolls this whenever they judge appropriate.