I'm not 100% sure what you are trying to achieve here, but you can keep the following in mind:
I see you are performing 2 REST calls, maybe this is why you get double data.
As for the units – I can see in your import mapping that the unit is not included. This either means that the attribute "Unit” is not included in the JSON, or that its not selected for the import mapping. If its not in the JSON you must add the attribute in there. After you've done that (or if its there already) you should select the attribute in your import mapping. You can do this by clicking "select elements” (see screenshot), select the attribute and map it to the attribute of the object you are importing.
Again, not sure if this fully resolves all your problems but I hope it helps!