From what I can see, the height is actually correct now. The WebViewer is filling the full vertical space of the screen. The remaining issue looks to be width (and your layout/container settings), not height.
The issue where the WebView only loaded the first time and then showed a white screen after reopening was not something you did wrong. That was caused by a recent Thunkable update. There’s an active bug report about it here, which matches what you were seeing:
If you’d like, DM me a link to the project and I can take a look at your setup.