Hi Sarah,
It definitely sounds like you had an OBE and OBEs frequently occur during sleep paralysis. Yours is the first I've read about where someone was so forcefully removed. Why you were so forcefully removed I really can't say, but I do have a theory.
I believe that there are different layers in the Astral construct and some of the lower vibrational layers are where discarnate entities linger after they pass. You can usually tell the lower regions because of the telltale signs such as difficulty in obtaining vision, everything is dim and gloomy and there is a general feeling of fear and apprehension. It could have been that one of the discarnate entities may have perceived your vibrational level and decided to give you a helping hand separating from your body. There have been many documented cases where people have reported something helping them to separate, like a hand reaching out to grab them and pull them out. Maybe the entity who helped you separate was a body builder in his past life and didn’t realize his own strength.

Once out, your consciousness knew that it could not, or did not want to hang around in that dark and dreary place and decided it was time for "higher ground" and thus you experienced what most people that have a near death experience (NDE) experience, the flight to the light, towards a higher vibrational area.
So, take this for what it’s worth. It will be interesting to read what others have to say.