2) For the mass audience, streaming solutions (99% of that being youtube), have completely replaced piracy. However, if you noticed, I'm not talking about mass audience, it stopped buying music anyway. I'm talking about Beatport, Juno — shops especially targeted at DJs, who have very different purchasing patterns, and usually different ways of learning about music as well. A significant part of modern electronic music labels have stopped doing digital releases altogether, going vinyl-only, and piracy is one of the main reasons.
In the case of most games, sales are steadily decreasing over time anyway - so it'd need to be a pretty marked step down to remove the possibility that they're simply following trend. It'd be interesting trying to account for that in an analysis.
Anecdotally, I have several friends who torrent games by default - but they legitimately wouldn't buy anyway (to quote "lol at buying videogames in the year of our lord 2016").
Regarding the ratio of purchases/downloads, the argument goes back to the usual questions: 1) if the torrents didn't exist, how would the number of purchases change (i.e. are those lost sales, or were they never potential sales to begin with); and 2) what's the promotion channel for indie bands? I purchased a lot of music because I heard about it from someone who had a pirated copy. Now at least we've got Spotify discovery, Google music tailored radios, etc. working for us, but it's still not a lot.