Spray him thoroughly with antibiotic Blue Cote before reuniting him with the two hens.
He might be much bigger but roosters often hold still when being pecked by hens, so the chances of them making his wounds much worse or even "eating him up alive" are pretty high if not using a repellent...
I think he needs some proper broad-spectrum antibiotics to survive. So when taking your rabbit to the vet tomorrow, take him too or at least let the vet prescribe/hand you a good one.