Thanks for the advice! Sadly, we only had 2 hours to spare at the end of the jam, which made it near impossible to make it any more fleshed out, like adding advanced enemies (even though I planned it). Also, yep- the boss is that easy: for a game jam making a boss too difficult could result in your reviewer quitting prematurely, so I made sure that it was easily beatable.
I'm not sure if my game-dev partner will continue this exact theme, but I'm planning on my eventual genuine Metroidvania game being set in the human body.
Thanks for playing :D