I didn't check everything but it turns out that all NPCs and even Eira and Seraphine are missing names.
For the softlock, try flying behind the library towards the invisible wall, then fly a little to the right until Eira looks like she's flying towards the hill or map's edge, and when it looks like she's actually getting close to either one, fly back towards the secret cave while staying close to the right side hill. Turns out it wasn't from flying too low, it's just flying to the right. My bad on that one.
(Also you worry me on the "which dragon statue" maybe I didn't find everything. It's the dream one that looks pixelated from afar and up close)
EDIT: crud this was meant to be a direct reply but I misclicked. Sorry!