would he have been charged? An actor is told the risks and mitigations of an act so they can fully throw themselves (sometimes literally) into the role. Would your average actor have pointed the "safe" weapon and completed the firing process during the rehearsal? That fact that the weapon wasn't safe when he was told it was, was not his fault.
As the producer, he hired someone to do a job according to standard. It's like if I, a car owner, hired someone to fix my brakes. When I hit the brakes, I expect the car to slow down or stop. I do not expect it to speed up. If I hit someone with my car while slamming on my brakes, I expect the brake fixer to be held liable, especially if I show the court my receipt for the repairs the brake person did. Alec Baldwin is shielded, to a degree, because he hired a licensed armorer to prepare the weapon and let him know that it was "safe."
The prosecution not giving him evidence that might have raised doubts about their case was just...not a thing to be done.