I do not have an Xbox, but will try to answer your question anyway.
If a download is extra multi-player or co-op then then it needs other on-line payers to be playing the map at the same time to have anything to shoot at. If you were to go in to the maps on your own, all you would be doing is wondering about with nothing to do.
With the PC we have lots of free content made by talented and not so talented armatures who make maps,both single player and multi-player. Obviously the single player is what it says.
As far as I can make out your game does not have any single-player DLC content, so unless you play multi-player or co-op, you are out of luck.
Why do you not have Silver membership? I know from another of your posts that you are not keen on paying.So silver would be OK?