He said he used 5% not 2.5%. I highly doubt RU can destroy your lungs, shortness of breath and lung/chest pains are side effects of many different medications and they don't mean something sinister each time it happens. The abundance of caution when using something unapproved and unstudied is wise, but not all sides are disasters.
I've taken prednisone before for an auto immune condition and my first week on it I threw up 25 times and had bouts of breathlessness as well. Doctors didn't even seem very worried when I told them, they lowered the dose and said keep going. I also got heart palpitations from 5% topical minoxidil that disappeared 2-3 weeks into taking it.