lawnmowerman,
Breakaway power is the amount of power used to start to get an aircraft to taxi,(ie breakaway from standstill).
This is a Boeing term used within their manuals.
As each environment/handling pilot will be different this figure i imagine would be an average used as a guideline.
The take off power hazard area i listed is for static take off power as used for ground running purposes,so in your example it would apply from the end of the runway(panio keys) .
If you have access to the aircraft mantenance manual the figures and warnings are listed in mm71-00-00-201 Engine ground safety precautions.Note the AMM doesn`t list exhaust velocities within the hazard area.
Regards DDG