I'm only seeing the -1 for 2 reference in the End Game scoring section. Can you clarify where you are seeing the -1 for 1?
To answer your secondary question - I've been taking the Tzolkin approach. Each building is essentially minus 1/2 of a point (for tie-breaking purposes).
I saw this too. It's in the rule book, and it looks like a typo. One line looks like it says -1/1, but the longer explanation seems to make it clear that it's -1/2. (I don't have it in front of me, I can look it up when I get home from work.) The cheater cards are clear that it's -1/2, though.