I set the cache to 1000 because it's zero left, so it stalls waiting for something to par/unrar. So why is the cache so full?
It makes no effort to return memory to the system. Once you've used all 1000 blocks they stay allocated and get re-used.
6.72 isn't like the older versions. It doesn't really need a large cache. If can download and unrar at the same time using as different mechanism.
At this point I'm not clear what you're reporting. You told Newsbin to use a gig of RAM and it's using a gig of ram for buffering. I don't believe that's what you really care about is it?
The question seems to be whether it's stalled or whether it's unraring and repairing.
Image posted after my replay:
Edit: You see where it says "DL:X" like "DL:7" that means X files are still downloading. You might want to hit the + icon and see if the files are showing red or black blocks. The retries are only at 0 or 1 so, it's not going to assemble and repair yet. If you have retries set to 2, it'll do 2 retries then it should assemble what it had and repair if it can. If you have retries set higher than 2, it's doing to take longer before it does a repair.
You might want to enable aggressive assembly mode in the options too.