Robert,
As you recommended, changing the layer url from the hostname to the dns entry in the config.xml resolved the issue. The identify tool now returns results from only the specified tax parcel layer when the onlythese variable is set to "true".
I was able to correct the following blank result on my own.
[ATTACH=CONFIG]23723[/ATTACH]
My sloppy coding caused the blank result to show up. Removing the carriage return between </layer> and </layers> did the trick.
I am using the web adapter, but when I remove the port number from the url, the map services fail to load. I'll have to look more into this. I'm with you, it is really annoying to remember to add it.
Thanks again for your help, your contributions to this community are invaluable. If our paths ever cross, I owe you a drink.