People who can afford a yacht do watch prices all day long. That's how they got rich, not by buying at any price.
It really worries me that the bastion of the market economies i.e. the US starts such a lot of trouble when markets need calm. Why he has to cozy up to the autocrats I don't know.
China can't really liquidate their US Sovereign Debt holdings - it would strengthen the Yuan which is what they are manipulating the markets to avoid. It is Party doctrine to maintain a weakish Yuan relative to the US dollar. And the Chinese media proclaims on occasion that the Yuan should be a worldwide reserve currency - but the Chinese government will absolutely not allow it to truly 'float' internationally like the US dollar or the Swiss Franc; so that's never really gonna happen. China is in a tight little box of their own making.
Russia selling net $80B in US Treasuries is nothing. Not a even a blip. The notional value of the US Treasury market that trades every day is massive - more than half a trillion dollars.
In fairness, 500bn is a bit high since it includes bills and TIPS. An honest number is closer to 375-400 bn. Also, depending on the duration of Russian holdings (maybe all they had was bonds, right?) they could have moved the market. In any case, this was a non-event.
Not according to the Fed. Look at the top row: Mainland China. It's possible that they re-balanced their portfolio convexity but their net holdings of US Treasury Securities did not decrease. Taiwan sold a few billion. http://ticdata.treasury.gov/Publish/mfh.txt
China is stuck. They have too much. What are they going to replace it with? The US is "too big to fail".