Why was he followed by the dog? what's its significance?

now we all see the dog for the first time when brad gets the beat up pick up and the dog wont get out. but that dog jumps out and into brad's"camino" without hesitation, its like its meant to follow him around. at one point i thought the girl's soul was in the dog and thats why the was with the old man in the end.

Another point, the old man's goons are the ones who stole the brad's car at the beginning of the movie. they had the dead body of margoliese's grandson plus the coveted pistol. why the hell did they act so wimpy when brad found them, this part is hilarious by the way, and he shoots the guy in the leg. In the end these are the men who knock him out and the freakin guy has a cane , i feel so bad for him , cuz he turns out to b so nice, but tell me , u honestly want me to believe that not one of those guys had a gun when brad showed up to retrieve his rental and the pistol. why hadnt they taken the pistol to their boss yet?

The movie is good but very frustrating, i mean , am lost as to the whole leroy thing.