Questions of enthusiastic, but confused viewer

I really like this movie, but I still find myself puzzled by some of the actions and motivations of the characters, even after seeing it about six times so far.
Perhaps someone can explain some of the more tangled twists of this movie.

WARNING: SPOILERS AHEAD

Does the crazy father, Tarver, abandon his original plan of waiting in ambush on the highway for the bikers, and shooting them as they leave town, to instead attack them openly in the bar? It might make sense, if you figure that he's been drinking a lot, because ( it all happens very fast) he suddenly seems to get the inspiration to pull down the one biker's pants, and wrestle him out of the mens room and fling him to the floor, and then turn to confront the other bikers.

I just noticed yesterday that in the moment before the insane father gets shot, you can see that biker Davis is actually holding his revolver, as the bikers angrily get to their feet to confront the crazy father. So when the first shot is heard and the father is hit, we assume it was Davis who shot him, until we see his teenage daughter standing in the doorway with a gun.

It's not clear to me if the crazy Tarver expected all the other locals to join in on his side, once he started a fight with the bikers, though one would imagine so. It's hard to say what might have transpired, because the whole scene is radically changed when the daughter suddenly turns up to kill her abusive father.

I find it interesting that not once in the entire movie is a law enforcement official shown or referred to. The crazy father seems pretty confident that he can get away with murdering the bikers, and it doesn't seem like the law is on its way, after the shootings, though one would imagine the cops would show up there after a while.

My other question concerns the sex scene outside the bar. Is it Hurley, the biker who was fixing his motorcycle at the garage, who suddenly begins making it with Debbie outside the bar? And why does this happen? Is she not as interested in her seeming boyfriend Davis as he thinks? Maybe she was tired of him. They didn't really seem very close.

Any thoughts? This movie is fascinating but sometimes a bit hard to follow. I even wondered if there was supposed to be a suggestion of secret homosexuality on the part of the crazy father, since he seemed awfully interested in watching that young biker pee, apparently getting a good view of the guy's member.


And when he crossed the bridge, the phantoms came to meet him