The current way to link a test case and requirement(s) is explained in https://jazz.net/wiki/bin/view/Main/RQMExcelWordImporter, in which it requires manual selection of requirement during exporting.
The feature of having the requirement id(or title) to be a part of xls file and use cfg file to export the link into RQM has been discussed. It is still under consideration in this RFE workitem:
https://jazz.net/jazz02/web/projects/Rational%20Quality%20Manager#action=com.ibm.team.workitem.viewWorkItem&id=126460

Please comment there so that it can be implemented at earliest.

Regarding export multiple testcases linking to multiple test scripts, yes, it is achievable but you will need to put test cases and test scripts into separate sheet for multi-multi links export. I asked similar question before in this post:
https://jazz.net/forum/questions/177517/rqmexcelimporter-export-multiple-testcases-each-with-multiple-test-scripts-into-rqm

Hopefully this helps.

Using the RM CSV export function, you can add the 'Validated By'  column to a view, and run the export.
This will add a column with the testcase "id: title" format (or corresponding test artifact depending of RM artifacts in the view) in the output CSV file.
RM does not provide functionality to establish Validated By links from a CSV import.

Here you can find some more info on RM importing and exporting using the CSV format.