iBoost works best when your device is mounted somewhere between vertical and tilted back about 30 degrees (in either portrait or landscape orientation). A normal car mount is usually spot on. Make sure it is mounted firmly as iBoost detects small changes in the movement of your car. If the device is able to tilt or move around freely then it will probably go AWOL.
The calibration step lets the device find out its orientation in your car, always make sure your car is parked on a flat road when you start the app. If you move or bump the device after calibration then start again fresh.
iBoost likes steep slopes about as much as your grandpa does. Because of the way the iPhone accelerometer works, tilting the device such as when you are going uphill can confuse iBoost into thinking your car is accelerating.
No.
Increasing this slider means you will have to accelerate harder to generate boost. Adjust it so that it feels right for your car.
Increasing this slider makes iBoost less sensitive to closing the throttle (taking your foot off the accelerator).
Definitely.