About the icon. Yes, thats a problem. I can see that. I am happy to make a new one or even better, replace it with one contributed by the community.
About ReadAloud affecting the theme. I actually added bootstrap to the plugin, and I think I should not have. That is probably overwriting your themes customizations. But if you look in the Read Aloud admin settings there is a setting there to turn not load bootstrap. Please try that.
About TTS. Its broken and it was always a bit tacked on. It is broken because it used Google translate to provide the audio, then it cached it. But Google Translate stopped freeloaders from doing that. There is another provider I want to talk to, but like Ben I am not actually sure about the pedagogical goodness of that. I will defer to Elton on that.
Regarding audio feedback. Its possible. My own experience is that you spend a lot of time making it, and the students don't bother to listen or don't seriously listen. But it all depends on your situation I suppose.