He’s small so just give free access to hay and a limited amount to pellets. For growing bunny I will feed them more pellets than what they will have as an adult.
Look at your bunny droppings and you will see if they are eating too much pellets or if the diet is good. The droppings should be round and yellow, they can have an darker color outside but should be yellow and sandy when crushed.
I’ll link a site about bunnies droppings (sensitive to pictures don’t read the first link):
I always use looking at droppings to judge if my bunnies are feeling good or if their any problem. You can easily see if something is wrong by watching the droppings and that’s what I use to determine on how much to feed plus the weight of my bunnies.