RE: You are missing the VITAL information of how many ozs per day
Good catch, and the answer is that he was taking on average; one to two(1-2) ounces per dose, as his dosage would vary according to his symptoms. And so I calculated that he took an average of six oz. day for a little over six years before seeing signs of Argyria.
As for the water, he claims to have only ever used steam distilled water. That said, I had the chance to test his solution and found it to be very good in terms of; clarity, stability, tyndall etc.
As for taking smaller amounts, I would agree with the consensus that it wouldn't likely be possible to develop argyria with teaspoon size doses. Though unfortunately, there are instances where such intakes are not sufficient to treat conditions such as with our subject in question. ie, when asked if he felt it was an acceptable risk to take CS this way, he answered absolutely, as the alternative was to die. And so on a positive note, I suppose we could conclude that the CS is keeping him alive in spite of the odds, and where modern medicine completely failed.
Though above all, I'd say the outstanding aspect of this experience is that he was completely cured of the condition. Which makes this particular account a first of first insofar as Colloidal Silver and Argyria are concerned.