Follow-up:
After a few weeks of no improvement to the problem (leaves on top remained tiny, leaves from the base kept growing), I decided to chop down the old limbs. I am glad I did, as I found all kinds of rotten/damaged stalks which I am sure were unrecoverable damage. Clearly I didn't cut away enough after the freeze damage event.
Hopefully the big root system will help the growth back up from the base, and turn it back into a nice looking (and big) plumeria over time. I also got a few cuttings from the top, which looked healthy.....so I will pot those, and add some young plants to the fleet.
