Use Adobe Launch to deploy the JavaScript to get rid of the authentication issue. Despite using launch, Content-Type, sandbox-name, and Authorization are the only headers that are required. Make sure you are on a correct sandbox and in the left navigation rail, click on Sources and open Accounts tab and click on HTTP API to select the row. On the right side, scroll down to the Streaming endpoint and make sure to copy it from there.

Check out this link to Adobe Target documentation on Authoring Targeted Content Using Targeting Mode - hope this helps!

What I meant by that is its easier to manage the integrations and know what integrations are present when you set that up in the Adobe I/O because what that's going to do is flag it as an integration with the Admin Console under "Integrations" Adobe I/O creates a technical user account for the integration when you set up an integration. That's what I said its easier to set it up that way through Adobe I/O.APIs