Arduino Servo is behaving strangely
The odd voltages might suggest that the servo isn't actually (fully) connected to the Arduino. As it's a diagram of the breadboard layout, not a photo, I can't say for sure, but on some breadboards the +ve/red and -ve/black rows are sometimes split in the middle. i.e. if you were to connect the Arduino's +5v to one end of the breadboards red row, and the servo to the other end, they might not be joined (same applies for -ve/black). Just a thought; apologises in advance if I’m stating the obvious.