I am certain that all of the above indications are correct. There were no lyrics to the original "Carousel Waltz" which was, I believe, played almost as a continuation of the overture as a background for the first scene. At least in the version I played in, Billy was never actually seen to have struck Julie. The abuse is instead mentioned in a conversation. I think it is a female character gossiping either with Nettie or within her earshot who says, "I hear that he beats her!". I also agree that it is too beautiful a tune to go without lyrics.