I might not understand you correctly, but here is my take on your problem:
It seems there is confusion between DLC and game updates. DLC generally are add-ons for for games to enable additional content to a game. This allows you to play additional "chapters" (for lack of a better word). Game updates are generally bug fixes, stability fixes, etc to allow for "smAoother" gameplay without adding anything extra to a game compared to what it is like hwne you purchased it.
As a rule of thumb, you can not get DLC if you have a jailbroken PS3, but you should be able to get game updates in the form of PKG's.
Hope this helps