personalitylovers replied to your post: “how is mike hurting himself a joke omg that wasn't even intended to be a joke guH”:
I had the same thoughts as you with that scene though it also made me like Mike more. Yeah what he did was a dumb move but this shows how much he cares about Zoey and how strong their love is to him. He'll do anything for her which is kinda sweet.
It was a dumb move, but who has never made a dumb move out of desperation? Like the piranha scene for Zoey, the boulder scene added a human dimension to Mike for me. They both worry about each other to a fault. They can get pretty foolish about each other, but they're human. They're teenagers. Zoey's in her first relationship, and Mike's possibly in the first relationship where he's been treated like a regular person, not a burden or an oddity. They want to make this work. They want to stop anything that would prevent it from working. And they will do the dumbest things if they're convinced it will help the person they love.
Mike was impulsive and desperate, and I'm sure he learned to not do such a drastic thing again. He'll get better, but you've gotta make mistakes before you can learn from them.