Is morality varied in the Mahabharata?

The response should be extensive and in-depth. There should be no personal examples, Everything stated should be supported with evidence from the epic (the Mahabharata). Answers should be outside the box, not flat or shallow.

The question is:
One of the innumerable ideas the Mahabharata proposes is that dharma (translated as righteousness in your show) varies and depends on the situation one finds him/herself in, as well as the intent behind a deed. Such being the case, some deeds which appear immoral become good due to the intention of the characters, whereas other acts which follow the rules are perceived as unjust. Take as an example the Pandavas marriage to Draupadi vs. the game of dice. All the accepted moral and social norms were broken in the former and all were followed in the latter (that is, the game of dice was technically in accord with the rules set out for it before its start). Yet, the polyandrous marriage was a virtuous deed whereas Duryodhans intentions made the dice game malicious. In this view of moral variance, how can one decide when a deed is righteous and when it isnt? If morality lies in abiding by certain rules, when do rules in turn become immoral?