iOS currently does not support ProRes. You would need to export H264 or HEVC for iOS compatibility.
We are working on a macOS app called LumaConnect, which would allow you to drag-and-drop virtually any media and that media would be made available to LumaFusion. In cases where the media wasn't compatible, it would create a compatible proxy which you could edit with, then when you're ready, you send the project to the Mac to render with the original media. This would hopefully resolve any issues with media (my guess is the 5120x2700 video might also be an issue with compatibility on iOS - though it is possible LumaFusion might allow it, in general iOS currently only supports 4K). We hope to release LumaConnect sometime in the 1st quarter of 2018
Wow. lumaconnect sounds amazing.