Chlorine dioxide is selective in that it does not oxidize healthy tissue. However, I have not been able to find any aerobic or anaerobic bacteria that it doesn't kill.
Only a couple of people have offered guidelines on how much to take. Jim Humble has several protocols, and Dr. Hesselink has suggested 1 mg of sodium chlorite per kg of body weight. Neither of these recommendations have any basis in test data, so I am not sure why they recommend what they do.
I might add that a virus is one of the hardest things for chlorine dioxide to kill. In the petri dish a high concentration is needed for a rather long time to kill the various viruses. For example the Avian Influenza A virus has a CT of 5000.