Valid points. I consider this a first iteration of the feature and would like to improve it over time.
adjusting the speed
This is definitely possible, I just have to figure out a way to make it usable on the user interface.
separate headings from its first paragraph
Have to think about it and figure out how to improve. Thanks for reporting
Great, so I also observed that,
Reacting to this
while using mobile phone, the reading doesn't stop permanently, it pauses and then continue despite not being active on the page. It only stops abruptly when you are using a PC. So maybe it's not applicable to mobile phones.