Hey Mike,
the G-code that the Buildbotics Controller uses…
where with G4 (Dwell), P is measured in seconds, not in milliseconds. That means your code lets the spindle pause for one and a half month.
Stop does not work during the execution of a command, so stop would work in one and a half month 
Better try this one:
Buildbotics’ software-based estopped mode stops any stepper motors, pwm spindles and routers connected via a relay on pin 15 (‘tool-enable’), and spindles on VFDs attached to RS-485 serial communications Modbus interface on pins 13 and 14.
Software-based estopped mode is available either on the red/yellow icon on the top right corner of the User Interface Display, or by attaching a button to pin 23 on the 25-pin I/O port. It is NOT triggered with the mushroom-shaped button on top of the CNC controller case.