Thanks for the continued help, Steven. I wouldn't be surprised if I'm exhaling too much air, in fact, there are times, especially on difficult material, that I will run out of breath early, so I can only assume that I'm switching to my reflexive breathing, which would be exhaling like I'm playing trumpet.
As far as the firmness of my upper abdominals goes, all I can say is that my abs/stomach don't contract unless I'm trying to sing really loudly, like pushing my vocal cords to the point where sustaining a steady pitch is really difficult. Otherwise, the area between the sternum and navel does get slightly firmer when I inhale, and the firmness continues when I sing a note. If I flex my abs I sound constipated. Maybe I am using up a bit less air when utilizing my "constipated mode," though?