I love the idea USA has no real debt as it can just print more, there is a cost even while printing more dollars every day to meet deficits and previous debt.  All holders of dollars will lose in devalued dollars if USA just prints for its debt.  That helps USA government as many holders are outside the country, its a form of tax on the world.
There is no free money though, efficency is a form of value creation in an economy and in its currency used but just printing ink on cotton notes does not represent an improvement in efficency or utility for the world.  The value of all dollars declines in this case but perhaps less then if government defaults.  Its hard to know what Trump will do exactly, if too severe he will accelerate this downward trajectory into a fall.  The market does not perceive this as likely

Yellen will stay the course of her term till 2018, the FED is not a government body.  Its not impossible she is dismissed but normally this should not happen even where each has a policy disagreement.
The whole reason Federal reserve can buy government debt is that it supposedly is a private bank.  Its nonsense but Trump risks damaging this castle in the sky if he should interfere too much.

The headline interest rate is different to the effective interest rate.  The market accounts for inflation, when inflation exceeds base rates you have effective negative rates in play.  Federal reserve may keep raising rates and still fail to pay more then the deprecation of the currency.
This situation is very positive for stable assets such as gold or bitcoin possibly if it can sustain its usage in a global economy not just USA