The servo driver and brushless motor driver SW now works as intended. The motor runs for 10.0 seconds and then stops instantly. I found (after much trial and error) that commanding changes to motor speed only works when placed inside the TMT1 interrupt handler instead of the main program section.
New handler shown below in case it may be of help to someone in the future.

Code:
;____This routine is Called on each TMR1 Interrupt______________________

T1handler:                               'interrupts are every 20 ms
           if sum <= MTtime then         'MTtime  = 10.0 second pre-set run time
           throttlepos = 400             'full speed pulse = 2.00 ms at 8mhz
           else
           throttlepos = 200             'zero speed pulse = 1.00 ms at 8mhz
           endif
            pulsout portc.5,throttlepos  'send pulse to motor speed controller
            pulsout portc.4,servopos     'send pulse to servo (pulse range is 
            Ticks = Ticks + 1            '1 ms to 2 ms for both pulses)
        if Ticks = 5 then
           Ticks = Ticks - 5
           Tenths = Tenths + 1
             if tenths = 10 then
               Seconds = Seconds + 1
               Tenths = 0
             endif
           sum = 10*Seconds + Tenths     'calculate time in tenths of seconds
        endif
@ INT_RETURN