I just skimmed the post for now but I will try to find time to have a closer look. I just want to let you know how it was intended to work. Great post, by the way. Really detailed!
- The slider in C sets the global playback speed. If you do not use per-podcast speed at all (probably a majority of users), you can set it to whatever value you want and all episodes you start will play with that speed.
- If you set a podcast specific playback speed in B, episodes of that podcast should start playing with that speed (no matter they are started: queue, play button, etc)
- If you are listening to an episode with podcast-specific speed and then move the slider in C, it will not change the global speed. What you set in this case only affects the current episode while still playing. You can pause and continue, so the speed is saved temporarily but if you play another episode and come back, it will use the podcase-specific speed again.