About the limited FOV, it can theoretically be increased up to 120◦.

From the paper: "The implemented FOV of the wearable prototype was 22.8◦ diagonal, which is far smaller than commercially available VR/AR displays. However, the FOV was mainly limited by the size of the available SLM and the focal length of the GP lens, both of which could be improved with different components. For example, the focal length can be halved without significantly increasing the total thickness by stacking two identical GP lenses and a circular polarizer [Moon et al. 2020]. With a 2-inch SLM and a 15 mm focal length GP lens, we could achieve a monocular FOV of up to 120◦"