Now in the world of titanium firing pins, dry firing without a snap cap may cause the firing pin to snap in half (got to love that S/A drops them in the Trophy match). If in doubt, a snap cap is good insurance.
As for the safety sear half notch, depending on the design (full width or center retention point to protect the sear), you may be able to pull the trigger to allow the hammer to drop/touch the firing pin from the half-cocked position.
The purpose of the catch position on the trigger was that if the sear had bounce/wear that caused the hammer to slip when the slide closed, this position prevents the pistol from an AD. Originally, the catch point was a carry over from the 45 revolvers, but with the thumb safety completely blocking the hammer from falling when engaged, the pistol full cocked with the safety on is the best way to carry the pistol when loaded.
As for the full width design, anytime the hammer is retained/caught at this position, slight damage does take place to the sear. This leads to the burs on the sear, and increased trigger pull for break point. If you have a standard service trigger (4-6lbs) don't worry about it. But on the other hand, if your have the trigger set to 2 lbs, this contact is going to make a short life to the trigger job.