Does AppleCare cover physical wear on MacBook Pros?
Is it worth taking it in? Absolutely! Apple have legendary customer service and will likely fix things they have absolutely no legal obligation to fix.

The power cord is absolutely covered. Apple will replace it free of charge under your warranty. As for the weathered keyboard key, they may likely do the same as that shouldn't be happening and a replacement key (which they will likely have a plentiful supply of in the back) costs next to nothing and is trivial to swap.

As for the scuffing on the case, they may shy away from that as that is a) a considerable amount of work to do and b) not cheap. But press them and you'll find that they may just acquiesce. The unit should after all retain its coating and they may tell you it's a "one time cosmetic replacement," but will still do the servicing.

I have personally had them replace my iPhone even though I couldn't reproduce the problem I had reported. My friend had his replaced, free of charge, after he dropped it and admitted to such when bringing it in (he is not alone here, as I have had other friends receive the same treatment). They also overnighted a new battery when my MacBook Pro was 6 months out of warranty!

I always encourage people to make use of their warranty. Apple's customer service is bar none the best in the world. Truly. They will make you feel like you own part of the company. I cannot express here how good it really is.

While you may not find precedent for them to fix any of those issues, you'll soon find that you won't need to. Apple works to make you happy, and not just to meet some legal requirement.