For updates, please go through support as they will be managing the case. I have emailed support regarding your case however.
I was having a similar issue with the new responsive form, variables and rules. I am developing a form to submit product parts orders. The form looks up the parts in another list (less than 200 rows of items) on the same SharePoint site and populates the associated data (list price, unit measure, part # and an image of the part) on the form.
lookup("Parts Catalog","ID",parseLookup(convertToString([Form].[Section IL 7000].[IL7000 Description]),false),"Part #")