Basic observation: Word for Android is not Microsoft Word full power.

This is true of all the mobile versions as well as the online version. There are many things that you can do with the desktop versions that simply cannot be done in any of the mobile versions.

It is really not the tool for editing a novel. It has only a subset of the features of the desktop applications.
Compare Word features on different platforms - Office Support
Word for Android is fine for reviewing documents and printing them. Perhaps minor edits. Not what you are doing.

You would be far ahead finding an old laptop with Windows XP and Word XP than trying to do this on your phone. Windows 10 and Word 2010 would be even better.

Yes. It is frustrating but you are trying to use a butter knife when you need a table saw.

Bottom line: I know of no way to disable the scroll bar on Word for Android.