I wouldn't delete Drive data from your phone. The syncing process requires some data to be downloaded on your phone. But Google decides intelligently how much, and if your phone needs the space for something else, Google will make way automatically. Bottom line is if space is available, Google's cloud apps will take it (other than Drive, Music is notorious for doing this), and then when you need the space back, it will automatically clear.
As for file size limit, it is 10 GB (per Google's support page), but remember that you must have enough space available on your Drive in order to be able to upload such a big file, and Drive+Gmail get 15 GB of free storage combined. How much storage do you have left on your Drive?