First of all, we are not allowed to use the arduino.h library for this project ...
I can't press forward without getting the int main function to work correctly before I start working on the I2C portion though.
Start by getting a simple blink program running, using your own main() definition and without using the Arduino core library.
When looking at arduino.h all I see in there is them actually creating the functions for loop and setup,
one will be on when the reading is >400mm and then the other will be on when it is less than 400mm.
A huge part of programming on the professional level is the ability to file serial numbers off cleanly.