If a hand wash or soap could be used to kill majority of pathogens that is on the skin, couldn't this substance be used internally to kill these pathogens should they enter the body and start a disease and as a result curing the person?

No because the activities inside the body is more heater and also the acid these is powerful to subdue the substance. Every part of human body has its own medicine meant for it in time of cure, that's why you cannot appear an ear drops to the aching eye.

answer; 4% i believe this is correct;

idk im very sorry i wish i could you