I'm going to punt this one. I debugged a bit in the simulator and commented out a line that actually does the drawing.
That shot it up to 60, but that is a) native internal code to NME/haxe and b) is already hardware accelerated. Contrary to my intuitions, none of the calculations or whatever are making it slow.
There may be some thing else I'm missing, but that's how it looks to me right now and doesn't look immediately solvable. That said, drawing text to fill up the screen is pretty intense.