Thank you so much for the kind words and excellent video playthrough!
Dodging the coffee is tricky and not very obvious if I'm honest! I'll give a clue, there are 3 'discoveries' (things to click on) that lead to changed dialogue when questioning the man (you got 2 of them in your video!). It requires all 3 for your character to be as suspicious as you were haha!
A warning though, even after finding a way to avoid the coffee it is possible to suffer the same fate...
Although the endings are nice little treats, the game doesn't lend itself well to replayability IMO so I wouldn't worry about it too much.