I am sorry to hear you are worried about Midnight. My name is Rebecca. I am a veterinarian and will do my best to help.
The little scabs you see and feel all over are typical for a cat that has an allergy to flea bites. You are correct, we do not have a cure for allergies yet. Giving Convenia shots, in my opinion, is a waste of time and money; it does not treat the allergic reaction.
However, we can treat for fleas and if he does not have fleas, he will heal and not have these scabs. There are many good, safe, effective flea products now, such as Advantage, Frontline, and the new Seresto collar that lasts up to 8 months.
When Advantage first came out, I was seeing a cat that was bald from neck to tail. The owners put Advantage on him, and his hair all grew back in when he started living a life without fleas.
The cattery can get rid of fleas, but it would take some work. Every cat in the place would need to be treated with the Seresto collar or Advantage or Frontline for at least a year. It would help to remove the cats, and flea bomb the premises as well.
Let me know what other questions I can help with or answer. Rebecca