Just cracked corn isn't healthy as it is only 7-9% protein.
You might consider giving him a gamebird ration or flockraiser type feed (20% protein) for nutrition. Cracked corn is good on the side as a treat or mixed into a high protein feed to cut the feed some. You can even keep him on chick starter/grower- that's what they recommend for the girls until they lay, and it's fine for roosters too.
I like to buy a 20% protein ration and cut it with all kinds of stuff (see my signature line). I don't feed very much commercial feed at all. I have 26 chickens that are nice and big, and I buy only about a 40 lb bag of chick starter per month because I mix all this other stuff in.
The cockerel will start mating when he is closer to 5 months old or even earlier from my experience. The hens won't be ready to mate until then, anyway.