[Ken Maltby]

Have you tried the "Show page overlap" menu setting? It will dim the part of the page that was shown on the previous screen(s). The overlap exists because the original page has to be displayed over more than one screen, at the settings you have chosen. And the last screen full will have only some new material to display for the bottom of the original page.

If you poke the bottom right corner you should cycle through the mini-progress bar options, including to dismiss the bar.

As far as I know the File Manager is always in portrait mode.

Luck;
Ken