Need help with PMT, PPMT and IPMT functions and calcs for Loan Repayment Schedule

There is nothing wrong. Simply write =-CUMIPMT(...).

Excel financial functions require signed cash flows: one sign for inflows; the opposite sign for outflows. It does not matter what sign we use for each direction, as long as we are consistent for each function. In fact, what we call "inflow" and "outflow" depends on your point of view: borrower v. lender.

I might use minus PV so that the FV function returns positive, but negative FV so that the PV function returns positive.

You write -D3 in most functions; that is, negative principal (PV; loan). IPMT and PPMT return the opposite cash flow. So they return the opposite sign: positive.

But we must write D3 for CUMIPMT and CUMPRINC; that is, positive principal (PV). Those functions are unusual insofar as they do not permit us to enter negative principal. (A design flaw, IMHO.) So they must return the opposite sign: negative.

Since you want to represent total interest (and all amounts) as a positive number in your tables (very reasonable, IMHO), we simply must negate the value returned by CUMIPMT and CUMPRINC.