When Gabriel reprograms the missile he keys in 'SMALLVILLE'. In reality, missiles are targeted with GPS coordinates, not by names.
When Chloe and Gabriel are fighting for the gun in the missile silo, the gun's slide is locked in the back position, indicating there is no chambered round, and the magazine is empty. However, the gun still goes off and kills Gabriel.
When Clark is shot by Gabriel, you can see blood come out of his mouth, but in the next shot, the blood on his shirt is already dry.