I would not trust the circuit for several realsons.
1. the sensor is run at DC. This will cause electroplatingon the electrodes and change the scale factor over time. The circuit should be excited by AC which does not have this problem.
2. I am not surprised at your results. The circuit should be a voltage divider to ground (5V, resistor, sensor, ground) with the pickoff the node between the resistor and sensor.
3. The emitter follower will then work properly.