Thank you so much for your very helpful and motivating review ! :)
I'm going to answer to all of your points progressively :
1. I had many more ideas like a leaking pipe wich would make the water level go up instead of throwing water out of it, or the fact that the water sprouts could force a valve or a cogwheel to move a specific direction to force the sprouts and conveyor belts to move.
2. The movement was in fact inspired by Jump King at first and then just became a way to force the player thinking a tiny bit before jumping to estimate where he would land (it's why the jump power isn't random), so it is a bit hard at first but when we understand a level it can be easier to reproduce the correct movements.
3. Thanks for noticing little details like that ;) at first I had to find a way to force the player stopping when entering a level because he would keep the velocity of his last jump before (wich made the game completely unplayable) and I also wanted it to not be abrupt so the player don't think the levels are jump random but indeed a path on the map (only the last one with the bottle of water could not be like that because I kind of missjudged my time and had to abandon a lot of levels).
Overhall I'm still working on the game as of today and I already fixed some bugs (like the one where the valves have a rollback when we go too far), improved the visuals, and added a save system for leaderboard. I hope it could be a cool little game later but I'm still very proud of it since it's only my 2nd game jam. :)
Thanks again for your help and the time you spent writing such useful and detailed commentary ! :)