So, I rearranged the layout *again* for the SEQ-16 PCB. It ate up quite a lot of time last week but the tl;dr is the autorouting program hit the brick wall on some of the connections and was churning away trying to solve impossible solutions for its ruleset. But in the midst of all that, I got a new boot drive for my computer. So I paused the PCB stuff for more than a day to take care of computer stuff (end result was I had to re-install Win10). Once my system was back in a useable state, I spent most of Sunday finishing up the latest layout. And success! The autorouter only took about an hour this time around. I stopped it at that point to manually fix the 4 connections it was having trouble with. Now the board is complete with zero errors, huzzah!
Next step is updating the matching faceplate, and then it's off to board fabrication (and assembly after that). Looking forward to crossing the finish line and putting this sequencer project to bed.