Steve,
I had a rod bearing go bad in a car engine once. I know this for a fact becuse I took the engine apart and could see the damage. All that was left of the rod bearing were thin slivers of metal. In my case the engine would still run (even at idle), it just sounded awful! I would think that this would apply to tractors too. A bad rod bearing will sound awful, and it needs to be replaced, but the engine should still develop power. After all, the piston is still moving up and down under pressure from combustion.
Now of course you mention metal chips in an injector. I don't know much about diesel injectors, but it seems resonable to me that something in the fuel system broke for these chips to get in. Is there a way to see if the injectors are still squirting fuel? I also like the idea of a compression test. It's easy to do and tells you a lot.
Best of luck!
Peter