For anyone enjoying this topic, a quick update.
I'm waiting for delivery of my trussrod. I will need to widen my slot, which I intend to do slowly with sandpaper. I'll wait for the rod. As I only want to remove the appropriate amount and not more, that seems wise.
Once I bung it in and slap the fretboard back on, the next job will be to repair the finish - or I'll be cutting myself when I play.
I know the Elders of the Build have a plan in mind for reattaching the board, I assume I need wood glue, which I have. But what (if anything) should I get for repairs to the finish?