I can get the servo to move the rudder left and right but it goes way to far and bends the arm that goes back to the tail.
What gyro are you using? You should be able to set your end points with your radio or with your gyro (depending on what gyro your using).
It also doesn't return to center when my TX stick is centered.
Sound like your gyro is in heading hold?
If you want to check your servo, plug it directly into your receiver (don't go through the gyro) and see if the servo work OK, that will tell you if there is something wrong with the servo.