Bozer tells Riley that Mac was told about his father leaving after his10th birthday party. In Metal SawJack says to Thornton that Mac's father left when he was 12.
MacGyver says he needs to burn out the circuit on Chin's scope to produce a stronger laser. So he uses a magnifying glass to fry the circuit. However, at that point, they are all taking cover at that time. So there's no direct sunlight for the magnifying glass.
Although the team is supposed to be in Hilo, the beach they meet up with the mercenaries is in Waimanalo on O'ahu. 'Rabbit Island' can be seen somewhat hidden by surfboards on the beach.