I DID IT!!!!!!!!!!!!!!!!!!
Allow me to preface this by saying how amazing circuitry is. I was completely uninitiated when I started this thread, but I didn't comprehend how a circuit forces you to think on a granular level, and then you actually begin to understand how all of these components feed off and control each other.
It turns out that I had some rewiring to do to make both toggles control everything just right. The wiring from earlier today was as follows.
Power from the 9 volt went to one toggle, which then fed the power to the thumbwheel and the BI pin. Sure, everything worked, EXCEPT the latching pin. I tried adding a second toggle that represented the master switch for the entire case, but I couldn't get it to "register" any number other than the first number dialed in when I powered everything up. I was forced to turn that second toggle off and on to update with the current thumbwheel number. However, that's not how the case operates in the film.
I then tried wiring the second toggle's power tab to the first toggle's output tab, in hopes that it would activate only after I turned the led on and reveal the number on the thumbwheel. That didn't work either. I've spent hours on this today, thinking about, and actually understanding (I don't know how that happened) all sorts of configurations until I finally landed on the right one. It wasn't a fluke or accident, it was the result of a deliberate thought and understanding of what I had wired up. I actually understand how this works. I still can't believe it!
The solution:
I needed a switch to the latch that was always on, but could be connected and disconnected from power at my discretion. The first thing was to reroute power to the thumbweel directly from the 9 volt, not via the first toggle that controls the BI pin (turns LED on and off). Having it connected to that toggle while trying to add another power switch for the Latch pin caused a problem where as when the latch was enabled, it only showed a 0 (resting state).
With direct power to the thumbwheel, which is distributed to the chip (minus the BI and LE pins) I wired both of those pins to the output of the second toggle, which is permanently in the ON position, then jumped power over from the first toggles output to second toggle's input. Now, when I turn the first toggle on to show the digit on the LED, it simultaneously turns the latch on, recording the current number. I can spin the thumbwheel all I want, but the number is already stored in the 4511.
When I turn the first toggle off, change the thumbwheel digit and turn that toggle back on, the new number is now burned into the 4511 register and displayed on the led!
Now I can set a 4-digit to any of the 12 LED readouts, flip the toggle for those digits, save that number in their 4511s, then change the thumbwheel number, flip a different switch and have a second unique number displayed on those 4-digits, and so forth. Up to all 12 readouts!!!
A MASSIVE thank you to everyone who helped, especially Brian. I'm certainly proud of what I was able to achieve, but without all of your combined knowledge, I wouldn't have been able to do it. And, we stayed faithful to 1988 technology, and most likely how the original was made.
Now to build 47 more of these, have custom plexiglass inserts made, then fabricate the actual prop. What did I get myself into?!?!?!
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Here's a video of it in action
**broken link removed**