That is a big important finding for you! That is very important. Holding the grip for your tennis strokes is a lot like holding a bird that you dont want to hurt nor you want it to fly away. You want to hold just enough pressure to so that if a friend were to pull the racquet out of your hands he could but with some resistance.
Very good! I am sure now your strokes will improve greatly! THe exception on the "sort of" firm grip is if you have a onehanded backhand. That grip is a more firm because the dynamics of the stroke calls for that.