Strulag,
#1 Once you have a idea were you want to mount the servo I use a small laser light . I place it at the location of the servo arm and shine it back into the fuse to locate the strightest line to the rudder control horns. Don't be scared to cross the cables if it will make the line from servo to rudder horn strighter.
#2 I like the cable to be at a 90% angle to the ruder hinge line
#3 same as #2 you have to find a compermise in the servo location and the control horns on the rudder but try to keep the cable at a 90% angle to the ruder hinge line
#4 I mount the servo output arm eather way but make my decision based on the wires leaving the servo in the best line to make it to the RX, also make sure your servo arms miss things when at a extreem angle.
#5 stock arm will do unless you go to the larger planes
#6 what holes do I need to put the cables in (at the servo and at the horn) Just make sure the cables are the same with apart at the servo & rudder horn.
#7 how do I test the tension of the cables inside the fuse once they are all installed. they should be to were the slack is out but not to were ther is actual tension on them.

If you don't understand something I wrote feel free to ask.
Roy
www.H.P.Pilots.com