If a node loses access, it will not be possible to communicate with the rest of the network.
Do you really think that icann will ban all domain names to "control" the network?
It is the same logic as proof of work. it is assumed that the majority is honest.
Probably no. But who knows ICANN will become better or worse over time. And the concern isn't directed to ICANN alone, but also various domain name provider (such as GoDaddy and Namecheap).
If proof of stake is possible using an asset from the network itself, why wouldn't it be possible to use an asset from outside the network?
At least for many PoS-based coin, the amount of coin is limited and people know how much rate of new coin generation. It doesn't apply to domain name.