Thanks for sharing your experience. It sounds like the author is aware that ProseMirror is hard to work with, and to some degree this is "by design". From the announcement:
> If you're looking for a simple drop-in rich text editor component, ProseMirror is probably not what you need. (We do hope that such components will be built on top of it.) The library is optimized for demanding, highly-integrated use cases, at the cost of simplicity.
> If you're looking for a simple drop-in rich text editor component, ProseMirror is probably not what you need. (We do hope that such components will be built on top of it.) The library is optimized for demanding, highly-integrated use cases, at the cost of simplicity.