Yes, the Jib Sheet is a continuous line, and Yes, it is much superior to two lines, because when you are on the windward side of the boat, the line is on your side of the boat. These boats are sensitive to your crew going to the other side of the boat to retrieve the jib sheet. It is difficult to be specific to the routing of the line, because there are several different configurations. All of them pass each end of the jib sheet through a block at the clew plate cleat and back to be attached, usually to the traveler car/block.
The stationary swivel cleat on the center of your rear cross bar is for the traveler. Your main blocks attach to the traveler car, and you main sheet and traveler sheet is also one continuous line. feed one end of your line through the staionary cleat, then pass it through the center of the traveler car and back to the eye strap on the back side of you rear cross-bar. The other end of your main sheet feeds through the block system.