Time to replace chainring?
From Sheldon Brown


  The normal technique is to measure a one-foot length, placing an inch mark of the ruler at the side of one link pin, then looking at the corresponding link pin 12 complete links away. On a new, unworn chain, this link pin will also line up exactly with an inch mark.


From what I can see in the second photo, the edge of the ruler represents the 12 inch mark, which lines up exactly with the middle of the pin on the end of (what I assume is) the 12th link.  The chain looks fine to my eyes.  (For what it is worth it has been my experience that KMC chains are pretty tough.)

The difficulty with using a ruler is also why chain wear tools also exist, these also include wear on the rollers as part of the measurements (which measuring the inter-pin distance will not consider).  Worn rollers will affect the realized pitch of the chain.

If your chain ring is too worn, the teeth will look like a shark fin and a new chain will slip under pressure.  For more info see: Does this chainring need to be replaced?  If your middle ring does go, I would suggest looking at replacing it before you change the whole crank set (Just my opinion!)