That's what I would do. He'd be perfect for EEs or OEs-- you'd get some nice colors in the offspring. You could use him with pure Ameraucanas if you like, so long as you told people you may sell the chicks to that they're pet quality, not show quality. That is all up to you.
Probably, but it could take a few generations. I would make sure it has the white skin color Ameraucanas are supposed to have as well. You can do that by looking at the undersides of his feet. White or pinkish white indicates a white skinned fowl. Any signs of yellow in that area means you have...
He is not blue wheaten. Honestly, his coloring is far from any standard, and I don't think he is a purebred Ameraucana. He has silver leakage as well as gold leakage. That wouldn't just crop up in purebred birds.