Okay, so here's something new to add to the conversation.
I should be clear that the bricks do not show signs of glazing, nothing is shiny or melted looking. The prior owner had kiln washed the inside to make it easier to clean between firings. So, basically, what is crumbling is that layer of kiln wash and some of the exposed brick. The bricks look very porous in some spots. I have removed chunks that were loose, but everytime I pass my hand over the bricks I get what looks like cookie crumbles. I am interested in finding out more about the Colloidal Silica (is this basically sodium silicate?)/Zircon mixture, but have received information stating that it would be too much of a "patch". The ITC is rather expensive (though, not as much as new bricks) and was told buy a kiln repairer that if I am not necessarily interested in improving the insulative value of the kiln, ITC is overkill. His recommendation was to use Rigidizer, which is $30/gallon and should act as the seal I need to keep these brick intact.
Any new thoughts on the subject? Not knowing the properties of these different formulas, I feel confused!