Rather than give up on this I decided to take a chance on saving it. It showed the same tiller profile after the crack as before so I drew it an extra inch to make the cracked part of the back raise and separate as much as possible, squirted wood glue under it, relaxed the limbs and lightly clamped down the raised part of the back. Shot it twice and it held (likely not for long, I know). Tweaked the tiller yesterday and heated out the belly set that limb had taken. I'm gonna keep going with it until it breaks. My question is could what I wondered before I ever started be true- that the back (I guess mainly cambium?) was so rotten/weak that it already wasn't doing any "work," which is why the bend didn't change after it cracked? Seems unlikely to me but how else to explain why the limb's bend didn't change with that break? Maybe I should have removed the cambium (and maybe the sapwood too) before I ever started.