It sounds like he just needs a little help finishing up his 'growing' process and will be releasable.Ok i have found a baby pigeon about 3-weeks old crawling around home depot crying so i brought it home and
its perfectly fine, i have had it for 4 days now it eats seeds and has been drinking.
BUT it is still scared of me it goes in a corner every time it sees my hand and trys to hit me with its wing and bite
From your description, he definitely has his defense moves (wing slapping and nipping at you) in tact.
Mom and Dad taught him well.
With that said . . .
I would suggest not lovin' up to him or expecting the same from him in return.
The best way you can help him is to offer him seeds, water and a clean place to rest his feathers and observe him, making sure he's eating, drinking, pooping and preening.
He will let you know when he's ready to be returned to the wild side of life.