A: Yes. The federal government can afford to buy whatever is for sale in its own currency.
A: Is there any other way?
A: That's not how it works. Taxes remove some of the money the gov spends into the economy. You could spend & tax the same amount. But the gov normally spends more than it taxes so that the economy can keep the extra dollars.
A: Except the $ to buy the bonds comes from the deficit spending! It's not "borrowing" in any meaningful sense of the word. When people swap $$ for bonds, they're just holding another kind of gov money.
A: The government retires bonds all the time. It's simple. You just debit (-) the seller's securities' account and credit (+) a reserve account. It's all done using a keyboard at the NY Fed.
A: Wrong. The gov makes interest payments the same way it makes all payments. It can always spend more on other things. Inflation is the limit.
A: All spending carries inflation risk when the economy gets to full capacity. If people are receiving/spending too much interest income, the Fed can cut rates. Or Congress can cut spending or raise taxes.
A: It depends what's in the GND and whether the US economy has the extra capacity to absorb the proposed spending *at the time it occurs.*
A: The GOP did well over $5 trillion in tax cuts and war spending without causing inflation to accelerate. And some GND spending will increase capacity, which gives you more room to spend safely.