As normal, I dont have the skills to help. Hopefully one of the "wizards" will chime in. If not, you may want to start a new post in the 3rd Gen Engine and Drivetrain -> 2003-2007 section because thats an interesting problem.

 

I have no (major) issues with Autozone, but the last time I had an alternator tested at our local store, it tested fine, when it was actually burnt up. Even after the test, I felt the alternator was suspect, so I took it to a rebuild shop. Toasted. I don't completely trust the testing equipment, at least at ours. That being the case, regardless what the machine says, 7 years old batteries are always suspect. Glad to hear that you have the problem solved. It is always nice when it turns out to be the simpler solution.