Thanks for giving it a go!
Ohhhh there's actually supposed to be a lasergate blocking the button that opens the cell to free your parents that doesn't deactivate until the monster defeated. I re-configured the map earlier and forgot to bring that back in. Great catch, thank you, fixing that now!
Regarding the grenade, I originally had it set to automatically execute once the player had it and interacted with the furnace, but another playtester thought it would be more satisfying if it was executed proactively by the player so I switched I switched it today. lol now I wonder if I should switch it back, I greatly value your perspective.