Poor guy. I am glad that you work for the vet and can get some help there. I agree with using chlorhexidene or Vetericyn, and plain Neosporin is good to keep it from drying out. The amoxicillan would be good. Normally antibiotics are not needed in many wounds, but that location with it being so deep, it probably needs AB’s. Polish chickens can be a target, especially getting head feathers pulled out, but he may have been picked on because of his age. I really hope that he feels more perky tomorrow, and will feel like eating and drinking. The meloxicam will be helpful. Let us know how he gets along.