Custom data connector schema

Hi, thanks for answering.
I don't think i understand well how metadata is represented in http headers.
The headers of the response are like this:

Unfortunately, the API is not Open Data, and my pq connector reaches out to a custom made WS to receive an Url, QueryID and Parameters.  Here is the connector code and result in json:
 

I can see in the TripPin example that we have access to a metadata column.
In my case, i see the data types of each JProperty in another JArray of the response, that i chose not to retreive in the Web Service, because the actual data is on dataSource. I have thought about fetching that dataType in the WS, but i don't know how to insert it in the result. Is it a good approach?

About the Determine Data Types function from the Power Query Editor UI, it doesn't get all data types right. My goal would be for the connector to determine the data types given any QueryID.

This is the first project of my internship, so i'm not yet very familiar with how data requests work.
Thank you.