Interesting to hear about the missing in-game speech, it's might be the same as the missing speech issue in Indy 4 that's been reported before. I think it might be resolved by changing the tooltype 'EVENT_CALLBACK_DELAY' to a lower value (see the readme for details).
The black screen 'issue' (and the nasty colors) that have been mention a few times now on the ECS version can be easily 'fixed' by updating the 'PALETTE_UPDATE_THRESHOLD' tooltype to a lower value, again the readme details what happens when you do this (eg performance drops!).
As I still don't have access to a real Amiga, I had to guess all of the default settings so they can probably be improved a little for the real thing, also each game is different, some games are happy with a setting which in another game causes missing cut scenes or missing speech so you'll just have to experiment a bit