That’s correct: Zero-ETH withdrawals on Ethereum
We are working on a next-generation implementation for our channels on the Ethereum network, solving one of the major pain points for users: the capacity to withdraw assets from state channels without having ETH in their personal wallet to pay network fees. The new implementation will allow for withdrawal fees to be deducted directly from the channel balance.
Not sure. But until then if you have used NashCash and trying to move the ETH/ ERC20 out from your contract to personal wallet , write to support. They will send you with some ETH that should be enough for the transfer.