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.
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").
It only pushes out the small companies and makes way for an app store environment where only large companies can survive. The exact same thing happened with the music industry over the past decade (filesharing was supposed to help the indy artist..or so many, like you, claimed)