I can't do much about the voices: these are from me and my wife speaking English, being us Spanish... So we have our microphone limitations are our English limitations
Also some people already told me that I need you let them to query the volume... I play with my speakers and the people who use headsets have problems with the volume
Don't get me wrong, I really like that you went the extra mile to record and include voice overs. :) If you would include volume sliders for the different channels that could help mitigate the different speaker/headset "issue" indeed - but I also know that would need extra time to implement, etc. I was debating that myself and it didn't fit for my timeline also.
