Why is it that I jump the same height running from far out and jumping as I do off a slow and short distance run up? how can I improve that?
It's because you don't actually benefit from all those additional steps. Taking myself as an example, when I was very "thin" (weighed 147 lbs) I used to jump very well off 7-10 steps of momentum. Now at 180 lbs I tend to jump well off 3-5 steps and actually jump worse from 7-10 steps because I'm more into accelerating into the jump now, whereas in the past I used a constant speed and jumped pretty much reactively at that speed, without force being an important factor. And obviously, I was weighing less.
It's still a matter of being able to amortizate properly in the last step, to prevent knee collapse and proper horizontal to vertical transformation of momentum, and for that you need strong quads and probably good calves.