Yeah, I'm not in the 'fcuk him with a cactus' crowd either, but I do think he needs to stew in remorse longer for justice purposes. I think keeping them in the misunderstanding is for once well deserved.
I want them to enjoy happiness together in the end, but not until she has enjoyed herself a little longer and enjoyed the support of her classmates (who are hilariously mistaken, but good on them for not looking the other way to the DV they are perceiving) and he has truly received the consequences of his actions a little longer.
That said, he doesn't deserve the death penalty. It is clear he cares about her, he's just a socially-inept musclehead who was clinging to his comfort zone too long and failing to recognize his obligations like many thickheaded teenagers do.
And also, he's not actually trying to take her happiness away. I don't know if anyone else has noticed, but she has to keep reassuring herself that she's better off alone. Like a lonely person tends to do.