Get servo to travel full length
This is an analog servo, so there is no endpoint calibration on the servo side. This type of calibration is for digital servos (which can be tuned) and controllers.
On the servo description page, they talk about a stretcher. This is a translation tool to help with old controllers:  usually servos have a narrower band: 1000us to 2000us for 0° to 180°. Therefore old controllers can only do 1000us to 2000us, and would fail to achieve full range with this servo, which requires 600us to 2400us

Also, note that RC servo input signal isn't really a PWM: duty cycle doesn't matter, only lengh of the pulse does.

Your servo doc says: 600us to 2400us for -90° to +90°, which correspond to what the Servo lib does by default according to its documentation. You should be fine. What are the results of a super simple sweep-like code? eg:

loop() {
  myServo.writeMicroseconds(600);
  delay(2000);
  myServo.writeMicroseconds(2400);
  delay(2000);
}