I'm confused about the safety. In the first part you say that the firing pin drops even with the safety on, then later it fires when the safety is pushed to fire position. Is the firing pin held back when the safety is in full lock; when it is safe but bolt unlocked; when the safety is pushed from safe to fire?
If it is the first two, then there is a problem with the trigger and the safety, but if the rifle fires only when the safety is in fire, then it is a trigger adjustment. If so, it may not even be altered and the fix may be just a thorough cleaning, or it may be adjusting the three little nuts that adjust the trigger pull. Finally, it may be as noted above and the surface contacts of sear and trigger have been reduced to the point that it no longer functions properly- if so, replacement of the sear or trigger is an inexpensive cost.