Summary

optimized version of the code.
it is supposed ATmega32u4 based board is in use, like SparkFun Pro Micro, Arduino Micro, Arduino Leonardo etc.

used pins:
buttons/switches - 2, 3, 4, 5, 6, 7
XAxis - A0
YAxis - A1
ZAxis - A8
Throttle - A2
RxAxis - A9
RyAxis - A3

pinout reference here - "cdn.sparkfun.com/assets/9/c/3/c/4/523a1765757b7f5c6e8b4567.png"