the screenplay made no sense

I am no screenwriter but I can easily tell when the flaws are this glaring. I'll put this in question form:
1)why when the townspeople's goal is to keep them in the house to sacrifice would Dave go out of his way to remind them of the frightening "history" of the house?
2)why when the friend couple came to visit and sense evil would they remain?
3)why was the reasoning behind the need to sacrifice a "family" never made clear and more to the point why did the house attack and kill others so quickly (presumably Bobby protected only his parents?) and why did they not count to satisfy the so called darkness
4)knowing the vengeful spirits if the house why would the townsfolk enter the house at the end? It seemed like they were ready to do it themselves but would that count?
5)why the *beep* wouldn't the townsfolk just move away?
6)when the son and his gf arrived she was clearly very creeped out by the house so why on God's green earth would she prefer to stay there rather than meet his parents in town??

These were just some of the questions that, to me, could have been resolved with a (longer) better written script. the lore was never explained and the characters motivations were flawed as all hell and ruined an otherwise decent movie.