the safety margin doesn't change when the safety comes off. It only changes when you rest your finger on the trigger. Using trigger weight as a safety is always a bad choice
Most data in these cases is related to law Enforcement. The elevated adrenalin levels involved in clearing a building, apprehending a violent suspect, and at the end of an extended chase whether it be vehicle or foot are more than you realize (Been there)
The most prevalent problems do not arise in the best trained but rather happen with those that accept minimum training. Someone carrying for self defense rarely trains to the levels needed to be totally able to rely on training and finger discipline to assure proper safety. It takes years.
Most involved in this type of scenario never realized their finger was on the trigger. Many have no idea how the gun went off. Fear is a very strong affect on what happens. Try searching an unlit building with a hand light and hand gun and see what it does to you.
I believe every option needs to be given to someone carrying for self defense. I have a little bit of experience and still prefer carrying a DA/SA Sig, a DAK Sig, or a DA only revolver. Having that added pressure needed is adding one more safety and requires a totally conscious effort to use deadly force.
When I did training, my biggest emphasis was you can never call that bullet back.
As much as I did not like David's book (Sorry Dave) I respect his data and I believe his data. John Farnum is also a very credible source.
To the OP, I gave a list of items needed for new carry and prices. Add to that list proper training. Going to the range with a buddy is good but it is not proper training unless your buddy is Ernest Langdon, Mas Ayoob, John Farnum, etc.
This is kind of going off topic so I will stop
Good luck to the OP on his search. No matter what you choose, I hope you never use it anywhere but the range.