Hi Pierre,
First I wish to say that it's a great honor to receive a message from you. :) I grew up on your Goblins series.
Forgive me if I was too technical - I thought you're familiar with the AGS engine.
To make the inventory window appear when hovering with the mouse cursor more closer to the top, you just have to edit the inventory GUI under the GUIs section, and to decrease the 'PopupYPos' property value. For example: if you set it to 1 then it will show up only when the mouse cursor's Y position is equal to 1 from the top (relative to the game resolution of course). If you set it to 10 then it will show up when the mouse cursor's Y position is less or equal the 10th pixel from the top.
Regarding the font - the font style is really a matter of taste. But adding more thickness to the outilne would surely make a huge difference.
As for the voices - making the voices lower in pitch would make them less "screaming" to the ears. But of couse this is a matter of taste as well. I only shared my feedback. :)
About the crash bug - forgive me but I'm not sure if you mean that it happens on your end too, or that you cannot reproduce it. I tried to re-play the entire level from the beginning and the game just crashed the same as it did in the first time. So I actually can't proceed any further in chapter 1.