as a follow up, my best guess at this point is that one character space in Times New Roman 12 pt is equivalent to 1/12" (0.83"). I realize that point is not the same as pitch, but with the given font settings I hit the space bar 12 times and it was very very close to 1" on the ruler, so it may not be an absolute perfect value but it's what I went with for now. Word doesn't allow 3 decimal places in hanging indents from what I can see, so I had to round a bit.

If someone has a better solution I'd be curious for future reference but for now I had to make a decision.