Oh my, I don't think that is anywhere near optimum. I use station pressure which on your Kestrel set you altitude on the baro screen to zero. Then just use the baro reading. That is station pressure. That is what I put into Exball. Leave the altitude in Exball set to zero. I also plug in the temp and humidity. When I get to where I'm going the first thing I do is set my Kestrel out on a stump or hang on a limb for at least 10 minutes to aclimate.
The altitude readings will not be accurate unless you set your calibration at a known altitude from mean sea level. I live near the ocean and parked within 8' of the water our airports elevation is 17'. My house is at 53' according to Google Earth. Once you set your known altitude in the baro screen you then take that baro reading to the elevation screen and plug it in. At that point you are calibrated for your area. The trouble with this is the baro is rarely perfectly stable. In a short time frame the altimeter will read pretty good but you need to check in periododically at known altitudes to reset the Baro altimeter height and then move the new baro reading to the altimeter screen to get it to match up. It you took it on a week long hike on a dry lake bed at an unknown elevation and you never had a reference point your elevations would vary by hundreds of feet.
Air density is good for tuning internal cumbustion engines. On a given day my Air density altitude will go from -2000' to 5,000' feet. Air density is a calulation based on barometric pressure, air temperature and humidity. If the Kestrel temp moves 10 degrees due to body or vehicle heat or the humidity is off due to being next to your body or in a vehicle or even in it's case it will throw the Air density altitude off hundreds to thousands of feet. Many ways to go wrong with Air Density Altitude. Exball is not calibrated for this anyway so I stick to the station pressure method.
There is a sticky on this topic here. Altitude vs. Barometric pressure