Of course, the whole congregation includes laymen and laywomen.
I've never heard of the Good Friday Gospel being sung, except in Latin. Did this woman chant it in English?
The priest sings it at two parishes I know of in Philadelphia. They are both predominantly African American parishes - not sure if race has anything to do with it. My own parish (predominantly Caucasian) very nearby these other two does things the usual way.
Yup.
The Passion is often sung on Palm Sunday. There’s no reason it couldn’t be sung on Good Friday—unless one were to judge that this is too “festive” for Good Friday. Personally, I think it would be. I prefer stark for Good Friday.