So, if he is 3 months old, he is not old enough to have that much tooth over growth from just needing to chew some wood. That is indeed malocclusion, so his teeth are misalinged. If he were a pet I would trim.
But I think if you are breeding for production, he is going to need to be culled, and a better buck located, as that is a genetic flaw. Option 1: you cull/harvest now, without treating for scabies. Option 2: you treat, wait the reccomended amount of time following medication, and then cull/harvest. Option 3: you treat, breed him to your does once, wait the reccomended time after treatment, and then cull, with the plan to save a buck from that cross--inspect all kit teeth very carefully.
Option 3 is not ideal, becasue I assume you have 3 sibling NZ rabbits already, so the odds of getting rid of the genes for malocclusion are low, and you will have to cull every rabbit that has bad teeth for generations. However, I remember how hard it was for you to find this rabbit. If options are limited, this might be your only path.
