It's ok to shorten the horns for more deflection, but it's totally unnecessary. You will never need that much throw, if you deflect the aileron enough for the horn to hit the bottom of the wing the plane will be rolling so fast it will be impossible to see it.

The angle of the pushrod to the hinge line is not super-critical. As you can see it's impossible to be square at all deflection angles. If it's square at some point in its trave you are close enough and it will work fine.

TF