Please wait for a response before writing a second Post - it is difficult to keep up.
The lines
LMotor = joystick[0];
RMotor = joystick[2];
copy the values from the joystick[] array into the two variables.
However your code seems very confused because later on it copies the same joystick[] values into LeftMSpeed and RightMSpeed
I suggest that the lines like
LeftMSpeed = map(joystick[0], 490, 417, 0, 255);
should be changed to
LeftMSpeed = map(LMotor, 490, 417, 0, 255);
That way there will be no danger of different parts of the program using different values.
You have not said if the values in joystick[0] and joystick[2] are the values you expect them to be. Maybe you should be using joystick[0] and joystick[1] ?
...R