Perhaps I'm a bit harsh, but I would have gone the route of; Sam kills the mother, gets either life in prison or the death penalty, and the kids go live with their father, even though he travels it would clearly be a better environment.

Perhaps the movie should have ended with Sam and his drug cronies machine-gunning the Livingston homestead killing all three. LOL
What the hell was wrong with Sam?! Okay, he was desperate to get the drugs so they could get the restaurant. Then he's all calm. And he gets more relentlessly violent than ever when the mother finally comes to her senses and Jake fights back. Looks like the cocaine really screwed with his brain at that point. If Jake had shot Sam a few times, Sam would have probably still fought him like nothing happened.

I really thought the older brother was going to kill him.

Have to agree with Roger, the ending was just plain silly. But I also agree with you that it would be difficult to end it much differently.
I'm happiestin the saddle.