My worse fears came true. He totally abandoned his dog and I took him in. While alone at home with me, he is the most animated lovable puppy. But as soon as I get company, he turns into a mean barking dog. You were very kind to take Spike into your life.
Most dogs have a protective side, but some chows carry it a bit too far.
This boy's problem is called protective aggression. He could become dangerous. Your boy likes being aggressive. To get control start having your visitors call ahead so you can put him in his dog crate in another part of your house. Never give Spike the chance to fall back into his old ways until you are both really ready.