I would first make sure you don’t have a defective barometric pressure device in your Air. I had several of those before WF was able to get the supplier to correct a defect in their manufacturing process. It’s easy to tell if you have such a defective unit by determining if your pressure is fluctuating with temperature.
As for humidity, there has been considerable discussion on Davis forums about issues with the accuracy of the humidity sensor that Davis uses. According to the manufacturer of the sensor, Davis is not handling them properly during the manufacturing process of the Vantage Pro and that leads to issues. What tends to happen is that when humidity is high, the Davis will tend to read too high as the humidity drops.
The VP humidity sensor also tends to read too dry when humidity is relatively low. So the bottom line is that the VP is not the best device to use as a tool for calibration. Some feel that having a fan aspirated unit makes things worse. On the other hand the VP barometric device seems to be very accurate.