Hi and welcome! Glad you enjoyed the game demo. About your questions:
1. This is subjective, I had other people telling me that voicing the thoughts was ok, but I agree with you. In my next game Heileen 2 (which has a female main character and completely different settings, but still interesting because of the seven virtues/sins) I'll voice only the actually spoken lines as you suggest.
2. Yes, you're not the first one that told me that. I did it with the food for example (you get the explanation on how all people were forced to become vegetarians etc only if you eat while you're in the kitchen). I'll remember this for future games (I don't think will change that in the game now).
3. Hm true, that's what the japanese VNs do, and should adopt a similar system.