How much pain should I be having with a crushed fracture of my back?

Severe. Everyone has a different pain level but fractures of the back can be severe and require fairly aggressive pain control. The pain will typically last for months but does decrease over time. If appropriate kyphoplasty for fracture of a vertebra can be quite helpful.
Depends. Perception of pain does vary from person to person. Pain also varies by the severity of compression, the amount of movement in the broken pieces, and the time from injury. In general, the movement decreases (as does pain) with the passage of time . It can take 8 to 16 weeks for the pain to subside. If it does not, consult your doctor.
Depends. The pain associated with a spinal fracture can vary. It depends upon the type and severity of fracture sustained. A compression fracture casued by osteoporosis can cause mild to severe pain. More significant, higher energy fractures like a burst fracture can be severely painful and can have associated neurologic symptoms, such as nerve pain and weakness/paralysis.