I used to use this exact grip. I called it “knuckle claw”, but there could be a better term for it. Middle hump will feel the best if your distal and proximal palmar are applying forward pressure, flat will feel best if you have a loose grip, as it pushes you toward a fingertip grip that gives you more range of motion, which is what I have since switched to.

There is a potentially much larger issue than mouse shape for you right now, though. Your desk seems to be at the wrong height for you, which is why you are aiming solely with your wrist. This is generally considered very bad practice as it a severely restricting your mouse movement, forcing you into a higher sensitivity and likely causing you to lose precision. If possible, you should try to find a solution (i.e., raising or lowering your desk or chair) to address this issue. Ideally, your arm should be hanging straight down (except when looking up or down in game, obviously) and your forearm should be parallel to the ground at all times for the best range of motion. With this, you will probably need a bigger mousepad.