I have about 7 remote datasets on my Xibo, all being created from Json files which are in turn created in Excel VBA to export live excel data into Xibo. To me, I would say it looks like you need to specify a data root (or starting point in your json output) for Xibo to be able to populate your colums correctly. I had to add some extra lines into my VBA in order to create a data root within my Json output, for Xibo to use the data correctly.
I will try and show you what I mean.
So my data root on my dataset is Xibo but it can be anything you want :
Then with the extra code within my Excel VBA, my raw json datafile has the following structure :
And when I click the Test Data URL button, I get the following structure :
Once this dataroot field is within the json output file and youve programmed your columns to match the data, it should work fine. I might be wrong on this completely though but it looks to me like the missing dataroot is the problem you are having.