dc.FileSave.ReturnMethod usually always returns 0. This means the configuration will not alter the return method of a document. EmEditor supports files that have mixed return methods.
If you want to find the return method of the current document and if you know the return method is the same in the entire document, you can write:
str = document.GetLine( 0, eeGetLineWithNewLines )
Then you can find what the return method of the current document is.
I hope this helps.
If you have further questions, please let me know.