I can't presume to say what would be best for all concerned, but in reference to some points made:
1. could you fashion some type of foam padding affixed with body tape or velcro to pad that outer edge of the wing where the callus is forming? It may be enough to help protect the area. If not, maybe to continue to allow the callus to develop will protect underlying tissue.
2. As much as roos may like to mate, that's not all there is to life (even for a randy roo!
Zane looks happy, healthy, he knows he is loved, and I believe SH has mentioned that he enjoys being outside in the company (but not in direct proximity because of the potential for injury) of the others. These things are all part of enjoying life in general. Zane seems to be accepting that although things are different and admittedly more difficult, he has not given up his desire to live.
3. I wonder if sometimes we may over-read our own sadness and sorrow at our pets' limitations or illnesses. I don't think, for the most part, that our animals respond to traumatic injury or illness in the same way psychologically that we do as humans. I think sometimes we may be a little bit too quick to say "it's time to let go". (NOT speaking of anyone specifically here; PLEASE do not take this personally, ANYONE! Anyone who has made the decision to be responsible for the welfare of a creature who is dependent on them has a great weight of that responsibility when it comes time to make the very difficult decision of when it is time to bring an end to that animal's life.) For example, a few months back, a friend of mine called me asking what to do for a cat that she assumed had been either snakebitten or poisoned. The cat had young kittens that weren't yet weaned. I could hear her howling and crying in the background like she was in total agony; my friend said the cat was having seizure like convulsions, couldn't hold her head up, had foam coming from her mouth, glassy eyes, etc. Seeing a vet out where they were at that time of night was not an option. My first instinct from what she was describing was that the cat was going to die, and was obviously in agony, and should be put down. I told them to make her as comfortable as they could, and to consider a way to euthanize her as humanely as possible. She decided to leave her in the basket with the blankets and just see if she made it through the night. I was certain she'd be gone and would have died a very difficult and painful death. Instead, by the next morning she was MUCH better, acting like almost normal with only some mild weakness. If they had followed my impulse, the cat would have been killed and the kittens would probably have died without their mother. I'm glad I was wrong.
I said all that to say this: Let your heart AND Zane's heart guide you. Don't be quick to let go because things are different. Animals adjust much better than we do to "different". If he loses ALL interest in life, and doesn't enjoy ANYTHING, including food, human contact, flock interaction and contact, and cannot or will not regain that interest, then it may be time to look at whether or not HE wants to live, but as long as HE WANTS to live, please let him have that chance.
Speckled Hen, you & your husband are in our thoughts and prayers.
eta to correct poor syntax