It is for us the living, RATHER(should here be a comma or no comma) to be dedicated here to the unfinished work which they who fought here have THUS FAR so nobly advanced. It is rather for us to be here dedicated to the great task remaining before us -- that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion.....
The above is a excerption of the Gettysburg address, so here's my two questions:
1. As I mentioned above, should it be with or without a comma after the word "rather". Actually, I searched on the Internet, it has different versions, some have a comma after rather, some don't.
2. The second one is, can the phrase "thus far" be replaced by "so far", if it could, doesn it mean that these two are totally interchangeable; if not, where's the difference?