Perform the routine every second day to give your body a days rest in-between workouts. This means that on week one you’ll be training 4 times a week, week two you’ll be training 3 times per week, and on week three you’ll be training 4 times per week. That ends up being 11 workouts per phase for a total of 33 workouts in the program. Also, during this program you will be taking one week off between each phase to let your body completely recover. You need to give your muscles time to fully repair in order to grow stronger and more explosive.
Use a smaller ball. It's much easier, when you're first starting out, to try dunking with a smaller ball. You'll be able to palm it more easily and control your approach, making the maneuver more satisfying and your practice closer to the real thing. Continue dribbling and shooting exercises with the appropriate-sized ball so you're not getting too used to the "wrong" size, but keep a small ball around for your sick dunks.
Using only a lifting (concentric) phase for strength training exercises could also be more effective for improving vertical jump height than traditional, stretch-shortening cycle exercises under load, for two reasons. Firstly, using only a lifting phase involves faster rate of force development through higher rate coding, and this may increase high-velocity strength more over the long-term. Secondly, doing stretch-shortening cycle exercises under load *might* cause the tendons to increase stiffness to a greater extent. This would make the muscle lengthen more in the countermovement phase of a jump, and thereby reduce muscle force for a given countermovement depth.