How to have the same key access multiple APIs

You can use the dashboard token API:

GET http://dashboard:3000//api/apis/{api-id}}/keys/{key-id}

This will return a token session object, in this case, the one created by the gateway, for the PAI ID you can use your dummy API.

Modify the session object to include your API, see the access_rights section here is the thing that needs to be extended to include the selections made by the developer:

{
    "api_model": {},
    "key_id": "54b53d3aeba6db5c3500000289a8fbc2bbba4ebc4934bb113588c792",
    "data": {
        "last_check": 1421674410,
        "allowance": 1000,
        "rate": 1000,
        "per": 60,
        "expires": 1423684135,
        "quota_max": -1,
        "quota_renews": 1421164189,
        "quota_remaining": -1,
        "quota_renewal_rate": 60,
        "access_rights": {
            "39d2c98be05c424371c600bd8b3e2242": {
                "api_name": "Nitrous Test",
                "api_id": "39d2c98be05c424371c600bd8b3e2242",
                "versions": [
                    "Default"
                ]
            }
        }
    }
}

And then:

PUT http://dashboard:3000//api/apis/{api-id}}/keys/{key-id}

{session data}

Again, include the dummy API as the api-id section.