Was there booing in the cinema where you saw Tosca, Barbara? Of course, the only time one gets to boo the production team is when they potter in on a first night (I'm usually surprised at how scruffy they usually are, not that I go to many first nights) and when they aren't there, the booing can, of course, be misinterpreted.
On "brava" (or indeed, "bravi") I tend to feel that it's "Look at me, I know a word of Italian that you don't know!" so I would never use it. But in Gianni Schicchi, Schicchi sarcastically sings "Brava, la vecchia, brava" (and a lot of extra abuse) when Zita tells him to get lost. How does that differ from "Brava, Madame Mattila" or whoever?