Are you sure he’s not trying to mate with her? When chickens mate the rooster will climb onto the hen’s back, which may seem like an attack. (And if the hen doesn’t want to mate, she’ll run away from him) I would suggest leaving them, but if there is any blood separate the hen from the flock.
Chickens will peck at almost anything they see whether they think it’s food or not. I’d suggest fencing off an area where the chickens can‘t get to where you can grow your vegetables.