Thanks, all!
I have good magnetic stud finders. Part of the issue was that the drywall screws were spaced about 8-12 inches apart, and some were very near the edge of the studs, so even a small miss on my part was enough. The other was that I mathed poorly, and only had about ½” of screw going into the studs for the first batch of screws I put in while I unpacked and tried to find the longer screws. Then I never came back and put in the longer screws. Looking at it afterwards, I’m amazed at how much weight the cleats carried without failing. I had seriously half-assed things, and it bit me.
There may still be some broken tools. I can’t see over half the tools that came down yet because they’re buried under the tills that I haven’t picked up yet. I have seen a couple dents in the flooring though, which probably would’ve been broken tools if I just had a concrete floor, instead of having spent extra for padding and then the fake wood flooring.