For your first question, you can use copy table to copy information from a secondary data source into your main data souce.
For your second question: Yes, you can submit data to a form library with some fields in the repeating table, and some other fields in the non-repeating table - you've to manually type in the xpath to the higher level field in the InfoPath to SharePoint List tool (or in the mapping.xml)
Attached a sample test form.
Hope that helps!