As for the controller bit, even if you change the controller, we can't revoke the .eth names. We can only change new registration parameters (as you mention).
We never intend to sell $ENS, it's a public good, not a profit-generating protocol. Think of it like an on-chain B-corp.
That said, if you really want to make sure you can't ever face the "egregious renewal fee" attack vector, you could just register it for a really long time. For most names, it costs like $500 to register it for 100 years.
The whole point of a DAO like this is to try to create good incentives for the project without central control.
For example, a website hosting child pornography I think would be quite detrimental to the value of the project. Would the ENS holders seek to maximize their economic value, or "property rights"? Or is child porn good for business?