As far as I understand and experience, tableau works with data. data dictionar is actually metadata.
not sure what you are trying to achive with combining data with data files.unless you want to impot the data definition. if yes it the wrong way to do it.
Well, they do NOT share common variable names.
In the Data Dictionary, you have a Variable Name column. In the Data file, you have an Apple column, a Banana column and so on.
You can't join those together: there's nothing to join on. Joins are performed on matching columns. You need to rethink how the data is structured.
Offhand, I'd say you need to get the question number into the "Data" file and join on that.