Boy, that's the trouble with so many competent bowyers on here. Too many differrent ideas... and they all have value. Frankly, most of them would probably work.
Looks like it boils down to 2 basic approaches, take it down a growth ring and hope the next ring has more integrity than the current back. This will lose quite a bit of draw weight, hopefully it will still have 40# or so. The other is to glue and wrap it the way it is and do the best with the tiller where it's at. The problem with this approach is that I'm always gonna know that I have a broken bow under there and I'll be waitin for it to break... never fully trusting it.
What about taking it down then adding sinew to the entire back? Might have to eliminate the flipped tips if I do that. How does black locust react to sinew backing?