Thank you very much for the feedback!
1. Some scenes in the story are available whenever the player wants to see them, in the right order, of course, but other scenes are fixed, like the art dealer appearing, the visit of a certain person, or Bernard coming to the riverbank with Emile on a Monday afternoon. The option of visiting the café unlocks when you go there either with Ferdinand or with Gilles. So my guess is you didn't go to paint with Emile that given Monday afternoon and missed Bernard's appearance? The fact that you meet with Ferdinand on Sundays doesn't affect that at all.
2. Definitely, a bug! Thank you, I'll solve that right now.
3. Emile's route ends when you get enough points for his good ending, so typically by the end of March. I'll add the option to go on dates with him more often during that last week of March, though, because it feels unfair that you asked him but you never get to see the date.