Thanks :)
Performance might be related to portals and that's going to be changed soon. I need to investigate it more to get all bottlenecks. The assets are not loaded but it might be very similar thing - many are created on fly.
The 2Dness is a problem. I tried going up and down and it didn't work that well. With the claustrophobic feeling I will be trying an approach that was recently in Shattered Lights (if you have VR for PC, try it, it's on Steam). And was also proposed by Vince. To scale movement and the space a bit. It should help with lower scaling up.
That solution that bases on eye movement would not work. I haven't try it as I don't have the tech, but it works best when moving slowl and looking around. I've seen people running in my game. The rotations would be really quick, too quick. Although I still would like to try it and be proved wrong :)