Get a mech keyboard if you haven't already, It made me, and other people I've heard, way faster. Use your wrist, don't worry too much about positioning because that sort of stuff doesn't really matter and just distracts you from tapping fast. Just practice high bpm maps, as fast and you can go, and focus on clicking the circles and don't focus on your hand. And you will get faster.
But I'm also wondering what speed you can tap, because at your rank you don't need to go over 200bpm to get ranks. Aim, accuracy, streaming and reading should be more of a concern that fast singletapping.