Hi Scamby,
Maybe try something like this:
created_at:<='{{ scheduledAt }}' AND created_at:>'{{ scheduledAt | date_minus: "3 days" }}' AND financial_status:paid AND fulfillment_status:unfulfilled AND test:0 AND closed:0 AND cancelled:0
This query field uses the the Shopify Search API Syntax in case you need to make any more tweaks.
Hope that helps!