Firmwares are named after the model name of your device, in your case ath79 is the platform name.
Using it as a wireless bridge will be fine, I'd highly recommend you to use WDS if possible.
NTFS is going to be slow and adding ReadyMedia (former MiniDLNA) on top of that wont fit within your available flash storage space. You can use extroot however to "expand" your storage space, however you will need to setup a swap file as ReadyMedia will usually use more than 128Mbyte of RAM while scanning media. All of this is more or less documented in the Wiki.