170 is something of a magic number for mashing. If you get higher than that, you solubilize tannins and can have astringent beer. The lower the temp, though, the less effectively you're pulling sugar out of the mash. Ideally, you'd keep your sparge right at 170F. This means adding water above 170F.
I'm no fly sparger, but what you describe sounds right as far as volume goes.