1. The population increase is not evenly distributed. It moves from east to west. If the poor, oppressed Canaanites were coming up into the hills, would they not be moving from west (close to the plains) to the east? But if Israel came in through Moab and Edom, then one would expect movement from east to west- which is exactly what we have!
2. Did the Canaanites magically stop eating pigs? Probably not. Other Semites in the area definitely did, as did people in Philistia. But for some interesting reason, the new settlers responsible for the massive population increase of the 13th century BC don't eat pigs. There are no pig bones in these sites or any other animals considered unclean by Leviticus 11. What you do have are sheep, goats, and deer bones- all considered clean under Leviticus 11!