You're off to a great start. I'm gonna skip straight to some advanced technique thoughts.

In order to have the greatest control over your stick, you want to make contact with the widest area of the stick possible while still feeling comfortable. To maximize rebound, you want to squeeze as little as possible. To maximize velocity, you move from the highest point of your stroke down to the drum as fast as possible, regardless of height. Those are the three ingredients for excellent sound quality.

It is difficult to add velocity without also adding pressure. As you are playing accents, ensure that you do not add an excessive amount of pressure to the stick.

In your left hand particularly, you should experiment with placing your index, middle, and ring finger further down the stick for better control. Getting comfortable with wider finger placement will teach you to play predominantly by turning your wrist. You do turn your wrist, but the motion could still be better.

Lastly, work on stopping your downstrokes lower to the playing surface so that you're able to place the following 3" stroke as accurately as possible (accomplish this by practicing slower).