Try to surf the internet for the cases when governments artificially held the exchange rates of their currencies (spoiler: Venezuela is among those countries) and guess what may happen with the "stablecoins", this thing is easily appliable to cryptocurrencies. Either the same will happen with Tether or they will have enourmous reserves to back the coin.
It is not a "scam" in a common meaning of this word but it supposed to work that way.
That's right. And try to find any proof about audit since last april.
I'm heard many times that Tethers team print out their currency without any control and fiat deposits.