I tried your demo and found a few issues. 1: stamina does not heal if you stop struggling at all. It is drained very fast once swallowed, and enemies can't be escaped at all.
The current stamina regeneration system checks if the player has struggled at all for that cycle. I think I will put it on a timer and make it a continuous regen effect for when you stop putting in inputs for like 0.5 a second. The current way the enemies are setup is very difficult. I am having a hard time finding a balance between challenging and unfair at the moment since obviously everyone's skillset is very different. So blanket difficulty settings is coming in the next update instead of sliders. Which means guitar hero style of difficulty. IE making the struggling only 5, 4, or 3 keys and making everything slower the easier difficulty you select and then making you choose a difficulty before you start is definitely coming.