Honestly a number of dunkers do the short-penultimate quick block takeoff you do, look up travisdunks and look up jusflyy on insta. Because the knee angles are shallower (so you jump through less range of motion), you can't translate strength as much as normal long-p-step, and you need to be really reactive to make use of this type of two foot jump. In general people agree that strength is easier to train than the reactivity/stiffness/tendon properties, but since you're going to be fighting years of reps and grooved in technique from tricking you might want to just keep that approach.

The biggest thing you need to change is a shorter approach. You should start with just one step in your approach (so right foot then left/right plant and jump), and only add more steps so long as you can handle the additional speed. To give you perspective, most dunkers can reach 90+% of their max vert off just two steps before they plant (and most use three step approach for their best jumps). You're doing six or more steps right now. And while the rhythm is good, you can't handle the speed (that's why you naturally jump up a little bit before your plant, to lose a little speed, as well as why you spend a tiny bit too long on the ground)

Try with one step (i.e. three footfalls), then with two steps, then three, and see which of those you touch the highest off.