Fantastic
The picture, though wonderfully stylishly drawn, is outdone by your description of Metroid physiology. Very interesting and very well done. It's always welcome to add well-reasoned science to video game monsters.
But I bet you can't explain Xenomorphs. All I've managed to think of to explain their exponential growth from chestburster to adult drone is the fixation of molecules directly from the air, perhaps by bacteria on their skin. Your move, Biologist.