Use a template column to concatenate, and then you can get your hash using this plugin.
You can use a template column to create the JSON structure. For the API part, it depends what the API expects. If it responds to GET requests, then you can probably use the Fetch JSON plugin. Otherwise, you might need to use something like Integromat.
I made a tutorial a while back that shows how to create a CSV export. Not entirely applicable in this case, but may give you some ideas about how to use a template column to prepare your JSON.
This is very helpful. Let me take a look into this a bit more. Is there way we can automate the sending of the CSV file based on time (at midnight) or does it require user action.