I do believe I’ve reached a point of having gone as far as I can do, with the current slate of ideas, until receiving materials from others. (And just updated the OP to reflect where we are.)
I was able to get the execution and underground scenes into shape tonight and add music to 3PO and R2. Starting the music right as 3PO wakes up from the memory restoration lets it end as the scene shifts back to the other characters and is a subtle way to include it. There should be some quiet moments with no music right after Yoda’s theme and the X-wing.
Oh, right, I still need to plug in the Palpatine music Cinefy sent me for the soul sucking moment. Okay, there’s one thing left for the moment!