One quick performance thing I recommend:
For your video overlay which slides on from the left, I would slide it in and then animate opacity. Combining an opacity change with movement might be what's making the animation jumpy. (It's jumpy on iphone 6 and ipad mini 2).
This might be what @strmiska mentioned, but video is sideways on iPhone 6.
The reading area is a bit small on portrait Iphone. I recommend scrolling the header image up when scrolling down. (Or making it smaller).
Great work and attention to detail! If someone showed me this document and said it was built with Hype I would need to see it to believe it.