If you can get the amount of ACTUAL files that you need to save down to around 200GB, you could then create a folder on your SSD, move the files there temporarily and then wipe the drive followed by moving it all back to the now clean drive, HOWEVER, it cannot be overstated that only fools or the uninitiated would ever ignore the fact that for any important data (And it must be, since you don't want to lose it even in THIS situation) whether it is gaming related, personal files from applications like office documents, movies, music, bookmarks, Windows settings or anything else that you can't stand to lose, you NEED to have another drive where that can be locally backed up so that when, WHEN, not IF, that drive dies, and it WILL at some point, you don't lose everything on that drive.
Same goes for the SSD and any important data on there PLUS possibly the very good idea of creating backup images of your Windows installation so THAT isn't lost if your SSD develops a problem or gets an infection.
Getting a third drive, whether it's another internal drive or an external one, should be high on your list of priorities right now.