So true! In the animal kingdom its survival of the fittest, the strongest keep the species alive.
However from a human perspective it can be quite difficult to watch our babies driving off those they don't feel fit in. Humans have too much emotion, both a blessing an a curse. :hmm
Oh poor dear bird, :hugs many times they are the lowest ranking because of health problems. The flock is good at detecting sick birds and of course bullying makes them weaker. Birds can be so mean to the lower ranking birds. :(
Normally it's a good idea to dampen chicken feed to get birds to eat, they love mash feed. But in his case we don't want him eating too much but we don't want him hungry either. So plain old dry chicken feed for now. He probably won't over stuff himself on dry feed. AND dry feed will make him...
Which birds get chased, who gets pecked the most, which birds are last to eat treats, who is last to roost, who roosts on the end or lower, who is last out of the coop, who cries all the time.... :D these are your lower ranking birds.
Until his crop is normal alongvwith his appetite, you might keep him from free range foraging as he may keep stuffing himself. Impactions are difficult to treat. Just water soluble foods like chicken feed only, it won't jam up his Gizzard. Yes, lots of water.
Oh and restrict and watch the amount of food he can eat, he shouldn't gorge and over stuff his crop. Small amounts throughout the day for a while. In a few days he should be good to free feed on his own.
Do you have any other cockerels? It's very common for pullets and hens to abuse cockerels and they will be relentless until he is mature. Find some other cockerel/cockerels he can hang out with until he is 6 or 7 months old, then he can be introduced to any of your hen flocks without issues.