I'm gonna be contrary and say I'd remove the fret board entirely, thoroughly cleaning all old glue from the neck surface and then replace the rod and glue down a new board. Why wouldn't that work? Why a new neck? I'd do whatever I could to save the original neck unless it was beyond repair or warped out of shape significantly without any rod tension.
If the fret board isn't fastened down entirely, wouldn't that explain why the neck twists with truss rod tension? I'm not trying to be overly argumentative, but I've saved a few crummy necks by replacing the rod and fret board.
The neck was so busted up on my 60's NR TB, I did just as I said. Replaced everything but the neck itself and it's a great bass now. Just a thought.