JK can chime in if any of this is wrong, but ...
doesn't that mean a very small number of people or entities have most of the XRP?
Yes, mostly OpenCoin and its founders.
Thus, if a sufficient market demand is generated and XRP reaches USD parity and provided there is sufficient liquidity, doesn't that mean that Open Coin Inc, is "fantabulously" wealthy?
Yes.
Is there a public list of who owns and how much XRP?
No, only which ripple addresses it's currently held by. OpenCoin started with 80%, 50% for "giving away", 30% for supporting itself. The founders held on to 20% personally. I don't know how much OC has actually gifted as of yet, perhaps JK can tell us.
Also, a different question: How do we know more XRP won't be created--faith?
Haven't actually studied the proposal but this would almost certainly not be within OpenCoin's power after the network gets fully decentralized. i.e. it would require a code change that supported the new coins being adopted by all the servers, and logically they would refuse to do so.