Despite what dog worship propaganda wants people to believe, dogs do not understand the concept of death and do not have human emotions. Therefore, a dog would not have PTSD from seeing its owner being killed by a bomb as it does not understand death. It also would not be triggered by flowers yet be perfectly fine around bomb blasts.
Even if you're on the Five-0 Task Force, the police will not let you just walk away from the scene of a fatal accident.
During the accident the airbags are not activated knowing that the car that Danno's drives is a recent model.