That is presuming private ownership effects won't be big. And they will be. China owns more corporate debt in the US than anywhere else and it is a high percentage.
Not necessarily. If the Chinese yuan is devaluing, Chinese investors want very much to hold US dollar denominated debt.
Yes, and so they would want to hold the federal debt. And also find ways to increase it. The GP post relates to China selling the debt to disentangle from USD.
Luckily there is massive domestic demand for US corporate debt.