I'd recommend getting a hydrometer calibration kit off of Amazon and a sensor that can be calibrated.
These allow you to get an accurate reading of the temp and humidity. The fridge needed to be set at 49 degrees F to be stable at an actual 55-57deg. Similarly, the hydrometer control needed to be calibrated and adjusted to hold at 75-78 RH. Without these devices I wouldn't have been able to do that.