[OwnedByJezebel]

There may be something he detects on the other side of the door that you can't. Maybe he smells something, hears something, or just thinks that something might be about to come through the door. I used to have a Yorkie that used to go nuts to get outside, like it was time for "fight club." When I opened the door to let her out, I could detect a very faint skunk odor. She could smell it indoors, but I couldn't.

When he starts to get obsessed about his tail, see if you can distract him. Get a toy, and give him something real to chase, and give him treats. He could just be bored.

And, throwing things in the air ... all of mine have done that. They will take a toy or a treat and they get in their own little world. It is suddenly as if the object becomes a living creature to them. They throw it, jump around after it, "capture" it, they throw it again (their prey is escaping!). On, and on, just self-entertainment with their "imaginary live prey." Completely normal.