| Quote #1
For though that Absolon be wood or wroth,
This quote says that Alisoun wouldn't even notice Absolon if he were crazy, so distracted is she by Nicholas. Madness here is held out as the ultimate attention-getter, a condition that makes a person into a spectacle one can't help but gawk at.
| Quote #2
This knave gooth him up ful sturdily,
The servant's banging and hollering upon Nicholas's door "as that he were wood" (as if he were crazy) is a foreshadowing of the madness John thinks he observes in Nicholas, and later the moment in which Nicholas and Alisoun run shouting into the streets.
| Quote #3
And at the laste he hadde of him a sighte.
A common superstition in medieval England (and today, for that matter) was that staring too long at the new moon would make you crazy. The image of Nicholas sitting bolt-upright, staring straight ahead is pretty creepy; you can understand why it would freak John out.