There was also no stated warranty at the time you backed (there is now), yet we replaced a device for you that failed, free of charge and without any hassle.
We have acted in good faith with you at every step of the process. I'm sorry it didn't work out in the end, but I'm at a loss what more we could have done. I think we've spent more money paying people to try to answer your questions than we ever took from your Kickstarter pledge.
That was something you chose to do, just like sending out devices without leases or contracts was a choice you made. I don't see how you have any legal grounds to request that he give the device back to you.