So the purple difficulty dice are the only dice with chaos stars. Blunderbuss has unstable 2: it blows up if 2 chaos stars are rolled. Ranged shot is 1d i.e. no way to get 2 chaos stars. Am I missimg something?

Difficulty of shot and defender being able to lay down purple dice.

If all you do is standard ranged attack, then sure, it may rarely come up, you will also rarely do anything interesting with you gun.

Yup, look at the ranged cards, some have inherent modifiers - or a defender with improved dodge.