Mike without making this too complicated, your problem with spring really isn't the IDY. Jeff put it in there to provide a bit of extra lift. This can help depending on the leavening ability of your natural starter. Leaving it in there likely won't hurt and leaving it out may or may not make much of a difference.
Lots of things can affect oven spring. Peter made a list of these variables here....reply #515http://www.pizzamaking.com/forum/index.php/topic,9908.msg104559/topicseen.html#msg104559
The 2 main culprits of a poor ovenspring are often lack of sufficient gluten development in the dough and/or the lack of a hot even heat distribution (the more even and hot the heat is the better). Without knowing how much starter and ADY or IDY you used before which resulted in poor ovenspring, another possibility is overfermentation. Towards the end of fermentation, I have found that excess acids can do funny things to the gluten matrix. It can weaken the the gluten matrix causing water to be release, toughen up the crumb, and lead to suboptimal ovenspring.
Whether you decide to use the additional IDY or not, your use of BF instead of 00 will give you a bit of a head start towards better ovenspring.
My recommendation for a 2-3 day cold ferment is to use around 10% active starter and just a pinch of ADY or IDY. Maybe 1/64th of tsp or less per 300gm doughball or so. If you are interested in oven spring, I myself would forgo the starter and just work with IDY or ADY for now. I wouldn't make the switch to using starters until you can make a satisfactory pie with desired texture and spring with commercial yeast. This way if you are unhappy with the results you are getting with starters, you can always fall back on your standard. This avoids a lot of fustrations IMO.
Whichever source of yeast you want to use for a 2-3 day cold ferment, I would keep the yeast on the low side. Once the yeast (starter or commercial or both) is dissolved in the water and flour, I would allow for the dough mixture to be out at room temps for about an hour or so to help kick start the yeast. Then you can go to cold fermentation. Of course the lower the temps, the more slowly it will ferment. Also depending on how much you use and how the dough is progressing, you will want to take the dough out to proof at room temps for anywhere from an hour to 3-4 hours before baking.
If you are willing, you can detail the recipe and methods you end up using here along with pictures and either myself or others can recommend when to pull the dough out or how long to counter proof before baking, base on how the dough looks to be progressing.
If you want a sample recipe, then let me know which yeast source you will be using and if you want to use oil in the formula.
Hope that helps,