I *may* have solved the problem for now. I can't recall if I read the "fix" here or on Apple's Community pages, but I set the watch on the charger, walked away. It was at 99% for 4 hours, but by hour 4 the watch was cool to the touch as if it was no longer actually charging, wheras after an hour on the charger it definitely felt warm. I then turned the watch off for 30 minutes. When I turned the watch on again, it showed 100% and seemed to drain at an expected rate. This morning when I charged my watch, it charged up to 100% for the first time in weeks. Removed watch and I am wearing it now and the battery reads 97% after two hours of wear. Seems like it's behaving properly. Now I wait to see if the issue returns or not.
I used to charge my watch via the USB port on my computer while working in the morning. I am no longer going to do this. From now on, I will only use the charging brick and cable (OEM).