Can you select a record's contents from a subform list to include in the main form? e.g. to select an address from a N&A subform list?

Yes. That is what we do in all the examples where we use a subform as a dropdown or search results etc. like this one.

http://www.dataease.com/DG3_BlogList/?ParentID=000...

If you want to select the main record based on the subform the easiest way is to simply put a button on the subform that set the selectionfilter.

http://www.dataease.com/dg3_HelpView/?PageID=13782&field1=*SelectionFilter*