I believe that plastic ring keeps it a little quieter up front.
Is the chain pictured on post #12 the current one, lubed with the wax?
Honestly, for 4,000 miles, it "looks" much older than that. IME, as noted, the wax doesn't work nearly as well,
IE, that chain, (IME), probably has more than 4,000 miles on it, (actual wear-by using wax)...
If you can swing it, I would replace the entire set.
(I am very anal about my chain and like FinalImpact, lube no less than every 200 miles)
With this chain having low miles on it, I think you'd be ok riding it more till you can afford the set.
This chain doesn't have 33,000 miles on it (which I would NOT trust). That's what would let loose
(not the sprockets) if something were to fail.. Just tolerate the noise for now.
*It won't hurt anything, just faster wear on this current chain with the worn sprockets (and the noise)