Would you be able to export that workflow and upload it here (or send me a message and we can coordinate offline) ? I'd be happy to take a look at the workflow and it's a little easier to do in WFA's editor.
I worked with sp_1008 offline on this one. The error:
"Failed to resolve expression 'getValueAt2D($ExportRuleSpecification,ExportRuleLoopIndex,1)'"
Was occuring as there was no row repetition setup, so the row index variable ‘ExportRuleLoopIndex’ didn't exist anywhere, hence WFA failing to resolve the expression.
The way to fix this particular issue is to create a new row for the create export rule command, have the row repeat based on the number of entries in your variable $ExportRuleSpecification user input, and then the syntax will work.
NetApp certified workflow ‘Create a Clustered Data ONTAP NFS Volume’ should have an example to work from – it creates the export policy on first row, creates export rules on row two and is repeated as necessary, and creates the volume on row 3.