A workaround would be to pass the referrer in the URL. For example, foo.com?ref=https://facebook.com. Then, grab the query param ref and set is as s.referrer value.

I would suggest running the desired report in Adobe Analytics Workspace, open Workspace Debugger, copy the curl request and convert it to Python code (using Postman).

Can you check if linksTrackVars are correctly populating in each click?

Can you run Data Warehouse report for the dimensions? It may be due to Low Traffic.

Raw data in Data Feeds are filtered with Bot rules. So, you will nto see bot hits in the Data Feed files. Customer Care can provide a day's worth data with bot hits, however, not sure if that would help. Is there any specific need for bot hits?

Can you breakdown the Unspecifieds with Device Type and see if they call go to iOS devices?Also, can you share sample image requests containing the product list from iOS and Android device?

Changing the allocation of the evar to Hit would indeed give you the desired results.