For example two by four inches tall and wide long wooden pieces that you can walk a guy off of into the sea from a ship. Or build a house out of

No wonder your leg hurts and has broken. The twisting force on the right leg especially gets even worse from being flat footed if you have very grippy shoes. The ideal would be to find how much you can reduce the sole to ground contact while always being in control. Because you have prior injuries i would start low sole to ground contact area testing and practicing with stand stills. Here's a smooth form thrower that is good to mimick even in driving, He's won a world title in distance throwing and the last time i looked i think he was rated 1033:
http://www.youtube.com/user/lcgm8#p/u/77/vHeMcsQdTLo at 10:13 you can see Jussi lean back with the weight and raise the ball of the foot of the right leg. Then he shifts the weight forward and steps through. This isn't the best video but the first one i found. On hole one in either the third or the second round with Jussi in the group that was being followed i think his approach was much better illustrated. But you should enjoy the whole competition anyway. Other people have good pivots and follow throughs of different styles in that video. Even team mates of Jussi.
Dancing, gymnastics and javelin might have similar motions to BH steps as well as martial arts.
For feeling i am looking for different things in training for different things. In competition mode i'm not thinking of the feet at all it must be automated. That's why field practice is needed -you don't want to be distracted from the task of aiming. For all out power i lift the need to be in balance and perfect control. You need both for the best result but there's the having and eating trouble with cakes as well as foot work. Yeah you could wind up with your foot in your mouth if you lose control

The easiest way to lose balance is to misalign running direction and planting position while planting and pivoting on a side of a single toe. The less ground contact you have the rounder the shoe area touching the ground will be. That means the least friction and fastest pivot if you are in balance and it takes all the chances of correcting for mistakes in the run up to planting position to tilted body at some joint and what have you. For any semblance of control for a ball of the foot pivot you need to have all the toes touching the ground so that you have the maximum amount of muscle power in stabilizing you. And correcting any misalignments. Heel pivot is more dependent on planting in the correct spot and not needing to correct anything.
The hip joint to knee to heel to toes angles are different between heel and ball of the foot pivots. Heel pivot angles and the used muscles are stronger so collapsing ain't gonna happen as often or easily. And if it would be on the way it would be easier to rectify if you can react quickly enough. And some reactions are automatic because as an upright standing species it's biological necessity to avoid falling so there are natural subconscious processes helping you.
The feel you are looking for is unobstructed flowing like water pivoting that isn't choppy or happen in stages if you use ball of the foot pivot. Stand still heel pivot is the same because the ball of the foot starts in the air. Running heel pivots come in stages and do have a jerking abrupt pivot (that's where the power increase comes from i think)but prior to that and after the transition from the toe landing to heel shift the foot needs to move without sticking to anything. There comes the need to stay feather light in the motions. And needing the movement control grace like cats or dancers. Being a former competition swimmer i get the lack of body control on land part. Wii Fit or other balance training is gonna help ever so slowly in my case. YMMV. I can't train that much because of the bum ankle. I'm on doctor ordered two week no DG and no excess steps break. Argh!!!
We have natural tees and slippery tees and snow and rain most of the year so slippery unreliable teepads are the norm for me. That is why i opted not to learn heel pivots around here because i slipped so often early in my career or the little toe hit raised obstructions and hurt and stopped the pivot and had me facing to the left of the target. Slippery conditions is the exception to not using super grippy shoes. That also means that i want to try to learn heel pivots eventually because they give a little more distance. That's the common experience of the best players in the world and has been measured and alluded to but published in the thesis of Öystein Carlsen. The caveat for me is that my bum ankle can't take many stand still heel pivots per day and x steps are even worse. It will take years to heal the broken tendon to possibly handle the stresses of heel pivots. Ball of the foot pivots stress smaller muscles and tendons from ankle area down more and risk the twisting of the ankle and the knee more even on good teepads. But i'm outta luck and stuck with that. No brace has allowed me to heel pivot safely so far. Although i just got an idea to test regarding that.
Flat shots need running on the center line of the tee and planting each step on the center line. Anhyzer needs running from rear right to front left with the plant step hitting the ground to the left of the line you're running on. Hyzer is the mirror of that.