1 You own all the "smirks" you make with Smirk. All the faces, the images, etc.
2 The sharing feature uses the iOS action panel, which Smirk uses but doesn't customize or have any insight into. Whenever you share something, I don't know about it.
3 Smirk sends crash data when it crashes, but it's anonymous and doesn't send any smirks with it. It looks something like this: