Here's good reference, which doesn't say explicitly you should not use it to break bolts free, but it does say very clearly you should
only use it when you need to make sure you're applying correct torque in tightening. It appears that every time you use a torque wrench, you're diminishing it's accuracy little by little, so it suggests using a regular wrench when you're not trying to assure a certain value, e.g. breaking loose a bolt.
It also says you should set it to zero after every use, because you're stressing the spring, and messing up it's accuracy. Keeping it set at a certain value continually stresses the spring, and it develops a memory which affects accuracy.
http://ecmweb.com/mag/electric_torqu...ches_critical/
Searching Google under "torque wrench calibration" yields a number of good articles. One suggests quality shops, especially engine-build shops, have them recalibrated every 30 days.