OK...you have something else going on here. As you say, your OS and applications should only be around 50GB.
For comparison, my 128GB SSD is right at about 50GB used. Win8 Pro, and
all applications (incl Office 2013).
So - we need to find out what is hogging all that space.
Hibernation - turn it off. That will free up several GB (equal to the amount of RAM you have).
Page file - reduce it to a minimum level. I use 1024MB min and max
Restore points - these can take up a lot of space
Windows Updates - likewise
An application such as
WinDirStat can help visualize where your missing drive space is.
And of course a full virus and malware scan would be in order.
For an SSD, you really need to keep around 10-15% free space, to allow TRIM to do its thing. For your drive, that would be 25-35GB.
To your actual problem - the OS and applications aren't taking up all that space. Something else is.