I've been told up to 40kg on the outside of Fraser is fine by a number of people. Definitely safe around the 20kg mark. Wouldn't touch that 50kg model caught recently hahaha.
Symetre, that vid is by the South African guys, one of their crew is a graphic designer, knows his shit!! We just lightly gaff them in the mouth, but our Namibian buddies (who make the excalibur rods and are pro guides) have said its perfectly fine to gaff sharks behind their dorsal fin if it needs doing.
As to removing hooks, big pliers, or one of those hook removers if you are hand at them. Just pay attention to what you are doing!