Alright, I visited the Genius Bar today and was very happy with the results. Again, I did buy Apple Care and this happened about ten months after buying the phone. Between the bad button and the figity battery, they just swapped my SIM card into a new iPhone 5 and sent me home to restore from my PC Itunes backup.
After the full restore, the phone is operating quickly, battery seems to have more staying power and the volume down button is working as is everything else. I still think the timing of the volume going out of control immediately after downloading the update seems suspicious. Still, wouldn't the problem persist if it were a true glitch? Hard to tell since I never did a restore from backup before taking it in. Also, could the phone's insistance on upgrading the software before doing the restore? I have no idea. I'm just a novice user with no real knowledge of the internal workings.
Best of luck to everyone else who has had this problem! Let me know if you think I can help.
Cheers!