IMO you are not giving him enough, and there are zero side effects from Colloidal Silver . The recommended dosage is 15 minutes 3 x a day. His smaller lungs will limit the CS being taken to what he needs.
IMO, you are also not giving him enough teaspoons. I would do 1 tsp 3 x a day. You cannot overdose Colloidal Silver even by taking tablespoons.
At the very worst overdosing (16 ounces a day) might cause his skin to turn blue over a several year period.