1) You lose servo resolution and torque if your arms require you to cut down ATV. So try to keep ATV up to 100% or more. More ATV means more torque and more resolution but slightly longer transit time. It's a trade-off

2) Assuming you want to reduce the surface travel, move the pushrod out to the further clevis positions on the surface. If you run out of positions there, then use a longer surface arm or start coming in closer to the pivot on the servo arm. Either adjustment will give you more power/torque on the surface and vice versa.