Re: 2560 x 1600 - About Time.
I could be wrong, but I believe font hinting, unlike ClearType, is not about compensating for low resolution. Its purpose is to describe the way in which the components of a character scale differently. The differential scaling affected Gutenberg too, though it probably took a few centuries before the rules were formalised.
As for the resolution achieved in the 15th Century, it was limited by granular phenomena just as much as today's pixel displays. The paper used was rough, the ink was grainy, and type matrices were not very accurate.