Bubbling is one of those things that is anathema to professional pizza operators and they go to greath lengths to prevent bubbling, like using docking procedures, bubble poppers, and warm dough. Yet many people love bubbles in their crust, and pray that they will get them and then fight over who is going to get the slices with the most or biggest bubbles.
Looking at the photos, you clearly have a light and open and airy crust structure, so the high hydration seems to be working. You didn't indicate how long the dough was refrigerated or how long you let it warm up before shaping, but somehow you got enough fermentation to improve the flavor of the crust. Part of the increase in flavor may have come from using more yeast. Maybe you didn't realize that you actually upped the amount of yeast in your recipe when you switched from ADY to IDY without adjusting the amount. IDY is a finer yeast than ADY, so less of it is needed when it is substituted for ADY. To convert from ADY to IDY, on a volume basis, you divide the amount of ADY by 1.5. So, the 3/8 t. ADY in your recipe becomes 1/4 t. of IDY. The IDY doesn't have to be proofed in water, as does ADY, although proofing IDY in water (warm) won't hurt it any. The recommended way of using IDY is simply to blend it into the flour. I assume that your Fleischmann's IDY from Sam's is the strain sold to professional bakers, not the so-called "Rapid-Rise" brand that is a different strain marketed to home bakers.
I might also mention that your use of yeast, whether ADY or IDY, is still a bit on the high side for a Lehmann NY style dough. The basic Lehmann dough calls for 0.17-0.25% IDY. However, using more, as I have myself done, has not posed a problem, so I don't think that that was part of the reason you didn't get bubbling, although it may have contributed to the overall flavor as I mentioned above. If you want to intentionally promote more bubbling, you could use up the amount of yeast even further or you could use a colder dough when you are ready to shape the dough into a skin. Bubbling will usually occur when the dough's temperature is below about 50 degrees F, although I have found a safer range to be around 57-62 degrees F. 50 degrees F isn't much higher than the temperature of dough that comes right of the refrigerator. One of the main reasons for the warmup period is to prevent bubbling.
A couple of other thoughts. You didn't mention whether there were any changes to your oven temperature. Bubbling is sometimes caused by an oven that is too hot. If you lowered your oven temperature from what you previously used, which might have been a logical thing to do since you were making a smaller size pizza than before, that might have prevented the bubbling from occurring. I have no way of knowing whether your kneading of the smaller amount of dough might have been a contributing factor to the lack of bubbles. What I often do when I make a small amount of dough, as in your case, is to knead the dough completely by hand, even for a dough using high-gluten flour like the KASL. It's just about impossible to hurt a dough kneaded by hand and you have better control over the condition of the dough when you use hand kneading.
Now that I have told you to do what I normally tell people not to do, it will be interesting to see Lehmann #4