My OH has an acquired brain injury and is now getting frontal lobe dementia type changes.
Things that the LA would pay for are carers coming in (up to a max of 3 or 4 times a day half-hour slots), day care, and befriending, but that will still leave you with lots of hours coping on your own. You could also get an OT assessment of your house to see if things like ramps, grab rails, bath aids etc would be helpful.
I am concerned, though, that you are thinking of looking after him even though his wife cannot cope. Do you know the reasons why she could not cope? In my experience, wives will do everything they can (and more) to keep their husband at home with them. Have you talked to the care home about his needs? One of the biggest problems with someone with acquired brain injury can be aggression and also disinhibition - although it very much depends on where in the brain is injured.
If, once you know exactly what you are up against, you still want to go ahead then you could try getting him to stay with you for maybe a week and see what it is like. The worst thing would be if you got your home, funding etc in place, brought him back and after a few days discovered that you couldnt cope either and he will have lost his room in the care home.