It was cold enough last week (-10) to use the balcony as the auxiliary freezer but it's back up to about 0 degrees with yucky frozen rain today. This morning, however, I finally solved the fretboard problem.
(Excuse the error with the coping saw by the diamond inlay, I was sloppy!) I coated the fretboard with a single layer of medium CA glue, smeared on with the back of used sandpaper. After letting it dry for a few minutes, I buffed it with steel wool and wiped it smooth with a piece of cloth. It's not perfect, but better than any test I'd done yet. I have to perfect the application of the veneers in the fret slots (you can see some spilled glue on one line). I have bought syringes that will hopefully solve that.