Trying very hard to understand this. (My picks--and reasoning--are below.) The argument was among / between Steve, Mike, and Arthur. (I say between.) The loot was divided among / between Dave, Gary, and Jessica. (I say between.) The loot was divided among / between the the burglars. (I say among.) The loot was divided among / between the three burglars. (I say between because the word 'three' is included.)
I agree with your choices. "Between" when there are distinct individuals, "among" when the division is less clear.
I use 'between' when there are exactly two choices, and 'among' with more than two or an indistinct number.
I agree with Stacy C, between should normally be used for 2 individuals. Among should be used for 3 and up.now if you are detailing a number, such as; divide this amongst the 3 of you. Amongst is used for defining a group.
I would agree with Stacy as well. I imagine everyone involved being physically in a room. If three people are all lined up in a straight line, the person in the middle is between. If there are four or more people, the person in the middle is among. In my mind, extrapolation to divvying up loot or whatever should follow the same rule.