1. In a fixed coupon government bond auction, the higher is the demand for the bonds:

the lower the yields will be at that asset maturity but this tells us nothing about the effect of fiscal deficits on short-term interest rates
the lower the yields will be at that asset maturity which suggests that higher fiscal deficits will eventually drive short-term interest rates down
the higher the yields will be at that asset maturity which suggests that higher fiscal deficits will eventually drive short-term interest rates down

2. When the government borrows from the non-government sector it eventually has to pay the bonds back on maturity. This will:

not be inflationary because the sovereign government just has to credit the bank accounts of those who hold the bonds to repay them.
be inflationary if the government payments to bond holders at maturity add more to nominal aggregate demand than the real economy can support given other policy settings.
be inflationary if by the time the bonds mature the economy is growing strongly so there will be too much money floating about.

3. When an external deficit and public deficit coincide, there must be a private sector deficit, which means that governments can only really run fiscal deficits to support a private sector surplus, when net exports are strong.