1 - The control horns do not have to be the same length, but you want them to be somewhat close.

2 - This is a bit of a misunderstanding - a typical example of taking a good idea to extremes. The point of using Ackerman is not so much to create slack as it is to prevent the wires getting too tight. Unless you have very large servo arms and control horns, there's really nothing wrong with putting the horns on the hinge line.

3 - They go AFT of the hinge line