I am so sorry. I will say that the Australops that killed her probably shouldn't be necked, but at the end that is up to you. I would consider rehoming for them.
As for the cockerel, I would just keep him separate and not infected, and he should recover in a week or two, however you should monitor him carefully. If you see any signs of infection, get ahold of a vet.
Also, others are commenting about your space, and I would have to agree with them. Chickens have to have a lot of space. Is there any chance you could let them out to free-range? My friend built a PVA pipe and chicken mesh walker box for hers to keep them safe but also ranging. Would that be an option for you?
As for the cockerel, I would just keep him separate and not infected, and he should recover in a week or two, however you should monitor him carefully. If you see any signs of infection, get ahold of a vet.
Also, others are commenting about your space, and I would have to agree with them. Chickens have to have a lot of space. Is there any chance you could let them out to free-range? My friend built a PVA pipe and chicken mesh walker box for hers to keep them safe but also ranging. Would that be an option for you?