Foxes and other wild animals have been raising teens for eons. Their dependents learn to fly in the dark, adapt to shifting environments and feed themselves. If they can teach their teens/tweens to survive on this planet, you can too.
He will be OK. He is ready, and he can do this, and it is going to get a lot better than it was today. That doesn't mean that this is going to be awesome. Growing up can kind of suck sometimes -- for kids and for parents.
I've been thinking that being a big kid mom is going to be different, but it doesn't have to be any less awesome.