I ended up in a different place after a similar experiment: I stopped trying.
Not out of defeat. I worked out that of the document work I was attempting on a phone, almost none of it actually needed to happen there. It needed to be read there, which everything does perfectly, and the editing was me filling a gap because I had twenty minutes.
The editing I did in those gaps was worse than the editing I did later at a desk - more typos, worse structure, and twice I made a change I had to undo. So the phone was not saving me time, it was moving time and degrading it.
Now: read anywhere, annotate anywhere, edit at a desk. The thing I install is a good viewer with comments. That is a much easier requirement to satisfy and it sidesteps the entire fidelity problem, because a comment does not rewrite the file.