Great info, razark! But surely, the hardest way to do it!
The offset dial for spread angles is easy to use with mere visual info gathering, once you understand it (and I only understood it here in the forum, recently by the way).
Basically, the targed "fills in" a certain ammount of space in your scope view. If your scope is centered and locked in the very midst of the target, that portion will be "0 degrees" in the scope, obviously. Well, the spread angle you want to set is the same ammount of degrees as the other portions of the ship appears in the scope. Then it's all about measuring the extremities of the target. So let's say the bow is at +3 degrees and the stern is at -3 degress, If you want to hit 6 torps in quasi-identical distances, you set angles for +3, +2, +1, 0, -1 and -2, and you will be hitting everything but the propellor (which would be at -3 degrees).
Obviously, the farthes away the target is, the less ammount of degrees it will fill in your scope. So if the ship is very far away it may only fill in "-1" and "+1" in the scope, maybe less, so for farther targets using the spread angle is probably unadvisable as you risc not hitting anything.