3. What is the point of him saying that the
Catholic church's councils "have often
erred [made mistakes] and contradicted
themselves"?

Yes it has . that is why fake news is such an issue

True blindness may be caused by trauma to the eye, severe conjunctivitis due to  ibr (infectious bovine rhinoceros) or pink eye or other infections, leptospirosis, lead poisoning, selenium toxicity, fungal infections, vitamin a  deficiencies, rabies, vitamin b12 deficiency, neoplastic of the orbit or  conjunctiva, cataracts, congenital malformations, etc.