i have not tried the export package. but I did discover something.
in the project I sent you, the simple one-scene one, turning on "Virtual Reality Enabled" (Oculus SDK) caused the problem to happen, but as soon as I turn OFF "Virtual Reality Enabled" in the Player Settings, the problem disappears, and the mouse aligns with the in-game cursor in play mode. What could this mean?
Also, now building my big project works, but then the game won't recognize the rift, and the app stays in 2d screen mode while my rift stays dark. possibly not related, but this happens now even with really old builds I have made of my game, from earlier versions of unity. When I play other, official, oculus store games, the headset is recognized fine.