If I were you, I would just try to stay out of it if I could. At this point, there are other people watching him, and he's got a chance to perform or fail. So if he fails, he fails. It's not your responsibility, you did the best you could. When he gets fired, wish him well and tell him nothing.
You know why I say this? Because I don't believe it's impossible for him to learn the skills you're talking about. Granted, I don't think he can learn them as quickly as you need him to learn them, in the kind of environment he's in. But I find it difficult to believe that the skills you're talking about can never be learned. So it might be best for him to be allowed to fail here, but keep on trying at similar companies until he finally "gets it." If it's truly his dream, he should keep trying until he gets it right... in as many places as it takes.
The longer you allow him to keep trying and failing here, the better his skills will get, and the better chance he has of getting the next job like this one. Although, if you feel that your own job could be in jeopardy if you don't fire him expediently, then perhaps you should hurry and get rid of him. But if you don't have to have him fired immediately, you shouldn't.