For future reference, those notches are stoned, not filed and done to a specific angle and depth. What does the sear on the trigger look like ? I'll bet the problem started with a broken or worn trigger sear. Send the gun tio Jim Martin or Lever Action Bill and let them sort it out. Both have the means to rebuild the hammer if needed. The hammer may be able to be salvaged without welding depending on how deep you filed the notch.