It's better to start applying Scrum by the book, and to really understand the underlying principles and values from the Agile manifesto, prior to customize it, so that the process does not get denatured. Be sure to run retrospectives at the end of each and every iteration (Sprint) to "inspect and adapt" your process and eliminate waste.
For your Scrum Master, he can track what is removed from the current Sprint. Also Sprints are planned based on the previous Sprints achievement, not on what was previously scheduled. I do no get its point.
