OK, everything is resolved! In two different ways!
So I should start with the actual solution to the original problem. This is going to make everyone mad...it was one yellow transformer wire that was plugged into a rectifier instead of the board!!! As mentioned before, I bought the OmniPL Retrofit kit, and when it arrived I thoroughly reviewed the install manual (I had actually read as much as I could online before, but it seems there are some differences in the versions). In the section where it talks about removing wires from the old board, it mentions removing both yellow wires, and I remembered that one wasn't on the board (since I had tried swapping the transformer). Interestingly, that's in the section for ProLogic and Aqualogic Plus, but not in the regular Aqualogic, which is what I have (or thought I did!). Anyway, before tearing things apart I tried just moving that yellow wire to the board, and boom, all of the old actuators worked! Checked the voltages and no crazy drops like before. So frustrating!
Well I was still excited about having the new board with wifi plus a lot more scheduling options, so I proceeded with the swap. The actual swap probably took 30-45 minutes, super easy. But I spent some more time mounting the display...since it's on a 15' cable I decided it made more sense to mount it inside my screen enclosure so you can control it without going out, and I had this weird hole in the wall that was covered by cardboard and it seemed like a great spot for it. But I wasn't excited about running the cable and having to drill through a portion of the house or the screen to run it. Well when I took the cardboard off, there was a wire in the hole that I wasn't sure what it was for. I then noticed that there was another wire I had never noticed before that ran from the pool panel into a hole in the side of the house. I realized this was an old remote display wire...they previously had a display right where I wanted it! The problem was the wires are bare on each end and I needed JST-XH connectors....but it was an 8 wire and I only needed 6...and I have a box of JST connectors...so surgery it was! Took a bit of time and had one lead break when plugging it in and didn't know till I tested (it powered on, but then couldn't communicate with the relays), but got it all in and now I have much better control of the pool!
Quite frustrating I bought 3 actuators, a transformer, and a new panel...close to $2k, and it was literally just one wire plugged in to the wrong spot. And a "pro" looked at it last year and didn't realize this. I tried to find some full wiring diagrams of this old board to confirm things were right but didn't find much. Surprising since its so popular. Anyway, I should be able to easily return the transformer, but the store I bought the actuators from say its a 20% restocking fee, plus I have to pay for shipping, so almost doesn't seem worth it. Thinking maybe keep them in case the others die (almost tempted to replace them anyway since the old ones are so grungy!). I also have one free valve control on the board so could use one more for something...just not sure what make sense!
Thanks for all the help!