What length should the shock leader be?
A shock leader should be about 1 and 1/2 half times the length of your rod and wrapped around your reel five times. (More than 20 feet of shock leader dqs you from IGFA records)
I personally don't use a shock leader unless i am throwing more weight than 5 ounces and i need distance.
I would however use a monofilament or flourocarbon leader anywhere from 18 to 36 inches. generally i use 30 inch leaders. longer gets more difficult to cast with.
Question # 3. I tie my rigs to the 30 inch leader using a snell uni or a pre snelled packaged striper / leader rig. The other end i loop and attach to a 90to 130 pound black barrell swivel by feeding the loop through and then putting the hook through the loop. The fish pulling on the line only secures this knot tighter IMO.
Question # 4. Flouro is fine but stiffer. and doesnt wrap as easy around the reel.
Question # 5 The fish finder goes on the main line (standing line) and is stopped by the swivel or i place a bead next to the swivel.
between two swivels.
There is no any one way. and others do it differenty.
Good luck and welcome to the board.