@ DEVICE pic16F676, INTRC_OSC_NOCLKOUT
cmcon=7 : ansel=0 : trisc=1 : posit var word : servo var portc.3 : low servo
main:
for posit = 1000 to 2000 : pulsout servo,posit : pause 15 : next posit
for posit = 2000 to 1000 step -1 : pulsout servo,posit : pause 15 : next posit
goto main

That should run your servo back and forth.
If it does, you've got problems with your POT input.
If it doesn't, you've got problems with your servo hookup.
But you probably already knew that.
Your offset of 350 might be wrong.
Try using the POT command instead of RCTIME.