film/dusting of reddish/brown material

Oxidation. I get it all the time on my Ninja, particularly after being riden in the rain (shows up a few days to a week later). It's a good indication that you need to clean and re-lube the bugger.

As for breaking, don't worry about it until you wind up adjusting it past the last indicator marks on the end of the swingarm. Once you have stretched it that far, it's time for a new chain and/or sprockets.

Cheers,
Brad

To be old and wise, you must first be young and stupid.