When Screen Reader is enabled, the audio switches to PCM. I does not switch back until you go to the audio settings and change it to Dolby. Add that to your items list. If I feed PCM to my AVR (5.1) the volume drops a lot.I discovered something about this problem.
As it turns out the screen reader's volume isn't excessively loud when you are using the TV's internal speakers, but add a home theater system or a good quality sound bar to your setup and suddenly the screen reader's voice becomes excessively loud.
The voice apparently has a lot of base content which the TV's rather tinny speakers don't reproduce very well. However a home theater system with a sub woofer or a sound bar with base enhancement will reproduce or even enhance the base content of the screen reader's voice making it excessively loud.
Text to speech voices are largely calculated to produce the sounds that make up the words being spoken. It may be beyond TiVo's abilities to modify the screen reader's voice to remove or minimize its base content. But it shouldn't be beyond them to add an additional audio/ video option to allow us to set the screen reader's volume similar to the way we can currently set the volume level of the TiVo's sound effects.