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Unfortunately, degloving is potentially very dangerous and basically untreatable at home. I would suggest taking the route of dropping him at a no-kill shelter where they will treat the problem. The biggest issue with degloving is the potential for infection in the brain due to the exposure of the spine to the elements. Fortunately, repair of this type of injury is relatively simply from a surgical standpoint, and recovery should be excellent unless infection has been introduced. As an alternative to taking him to a no-kill shelter, many vets are willing to treat and place 'found' pets (I know my vet does it routinely), and since you apparently have a good working relationship with your vet, you might contact them, let them know the situation and ask if they would be willing to take the cat and treat and rehome him. I know this is very common in many communities and I wouldn't hesitate to ask my vet to do this.
Other than pouring peroxide or other germ killer on the open wound, there is little you can do at home for this boy until the area is covered by skin.
Please let me know if I can help further.