We have a tnread here about freezing greens. Most people found out it turned to mush but still useable. Drying out is another option. But it your sulcata doesn't like hay it might not like dry grass. Try blending hay in a blender till it is fine then add a liitle bit. Over time slowly increase...
No matter how many I put down my RF maynard eats the whole flower. I would imagine the pistil tastes different then the rest of the plant, probably sweeter.
You do not want to use bottom heat with a tortoise, unlike snakes a tortoise needs heat from above that is where all their blood vessels are. As for eating give him some time and offer food everyday. Sonner or later he should turn into a little piggy