Corrected entry: "Captain" Lee Crane's uniform insignia denotes he is a Commander. The insignia for Commander is the silver leaf cluster, which he wears. The insignia for Captain is an eagle. On those occasions when he wears his dress uniform, his shoulder boards have three gold bars, which is the rank of Commander. A Captain's shoulder boards have four gold bars.
Corrected entry: Captain Crane orders the Seaview to come about 360°. So Crane ordered the sub to turn back to face where they were facing originally.
Correction: The degrees aren't an instruction on how far to turn, it's a final bearing. 360 just means turn due north.
Correction: While you are correct in your description of the insignia your premise is flawed. Captain, while a rank in the Navy, is also a title bestowed to the Commanding Officer of a Navy vessel regardless of rank. So calling a Commander "Captain" is correct if he is the C.O. of the ship or boat.
SantaJim