cool idea to couple ingame actions with mass and essentially linking shooting, jumping and size together and making lost parts become pickups again was so smart to make the player think about where they jump and shoot. there is a bit of a design challenge at the core of this design though and you probably stumbled across it while designing your levels:
by making the slime necessary to make certain jumps you had to place slime everywhere in order not softlock player progression, which in turn made puzzles based on slime scarcity rather impossible. you could force the player to loose slime in order to control the maximum slime they can have (as you did with narrow passages) but you could also have something like a slime dispenser, that alwyas fills the player up to 2 slime or whatever, so you can design more puzzle like rooms where the player really has to make use of the limited slime they have available.
sorry, if I'm rambling. your game put a lot of thoughts in my head ;-)