Very large players usually do OTC (over the counter) deals to avoid slippage and avoid exchanges. But i believe there are quite a few whales that trade on exchanges as well, though i think those volumes are mostly done by a large number of players, triggered stop loss chains etc.

You generally do not see so much traffic going into and out of exchanges. The majority of those volumes sit in positions that get executed once the chain is triggered.

They are trialing dex for some years now :) If they wanted for it to go online it would have been there already. You simply do not cut the money branch you are sitting on. That would be stupid from business perspective.

And even though i doubt BTC will hit 1 million anytime it's not the matter of the price of BTC but sheer volume of trading. So to speak BTC price does not influence trading volume, hence their commission fees on the trades :)

They are in such a sweet spot of the market beating around bushes and trading back and forth that i am sure they take a significant part in market making and price manipulation for sure :)

Think of funds available to Binance. They effectively hold all the crypto currency people entrust to them by transferring to the exchange. And then again, since binance is not a blockchain based tool, they can simply "pull" a few thousand btc from thin air sell it and then buy it back at a lower price and restore the balance :)

I really believe that a big share of their income is not based on trading fees but the ability to manipulate the unregulated market :)