The answer is yes, they can, and it does happen. Eye Displacement is a real medical condition called Proptosis. Short-nosed breeds, called Brachycephalic Breeds, have very shallow eye sockets and with the right (or wrong) kind of pressure or force, the eyeball itself can be dislodged from its place.
The answer would have to be NO. Other than complications from other eye related problems, or mechanical injuries (which they are more susceptible to), Pugs are not at larger risk of blindness than most other breeds. In fact, Pugs are not even one of the breeds most affected by a genetic condition called Progressive Retinal Atrophy (PRA).