In the docs, obtained by TMZ, Prugo claims he provided assistance in cracking the case -- assistance cops even said was "nothing short of remarkable."
Prugo says he had an "implied contract" with prosecutors -- in return for his cooperation, he'd get a plea bargain. But Prugo says "the prosecution has chosen to exploit Nick Prugo's cooperation" -- instead of offering a plea bargain, Prugo claims prosecutors used the info he gave them to file additional charges against him.
Prugo and other alleged members of the BB have been charged with burglarizing the homes of various celebs, including Lindsay Lohan, Paris Hilton and Orlando Bloom.
Prugo also says in the docs he's received death threats from Jonathan Ajar -- aka Johnny Dangerous.