The situation with Ethereum is very poor. We are waiting when his problems with ddos & next hardfork will be solved. We need his stability to launch.
Is this project in anyway dependent on Augur? Is there a point at which Ethereum instability may force you to consider a different platform?
Nope. About Ethereum: yes, if Ethereum will not be more stable we will think where to move Inchain.
Any suggestions?
Maybe Lisk? But I don't know if it meets all your technical criteria. Lisk is a backup solution considered by Iconomi team.