I managed to track down the culprit, or at least one culprit, of the non-start issues to my battery terminals. They're corroding much faster than I've ever seen before. The slightest bit of moisture in the air and I have lumps of corrosion forming. After a few days of this, there's enough corrosion buildup on the terminals and posts to halt the flow of steady current back to the battery. I had Advance Auto clean the posts and I did the best job I could on the terminals. The dash reads 13V again and the car has started ever since. Let's hope it's just that.