Do you have any layer feed? That is an easy way to give him some calcium. Or you could cook up his scrambled eggs with the egg shell mixed in.
I just read the whole thread. Very sweet video. I know how it is to feel very bonded when nursing a bird back to health. It is amazing that they seem to know that we are trying to help. He is a very handsome Old English Game rooster. I think someone else on this thread mentioned that he has Red Pyle coloring.
I copied and pasted info on asprin if you think it might still help:
Aspirin - for pain relief. Dosage is approximately 25 mg per pound of chicken's body weight each day (A standard baby Aspirin is 80 mg, and a standard adult Aspirin pill is 325 mg). This information is from the Poultry Podiatry website. Warning: aspirin thins the blood and should not be used if internal bleeding is suspected or in cases where a wound will not stop bleeding.