That is very odd. I've never had a crack run off the limb quite like that on the back. I've had some on the belly do that, but in those cases the cracks were already there when I started the bow, just not visible until I got close to the finished thickness. That belly split would not bother me much at all unless the wood starts to distort between the crack and the limb edge under compression. If it does, you'll have to wrap it. Those back splits are very troubling. The cracks I've gotten as wood dried were not dark, only water damage cracks have been colored like that for me. But, this can't be water damage or it would have been obvious when you started. As to what you should do, I'm not sure. I'd try a wrap or backing of some kind, probably sinew backing because that's what I'm most familiar with.
Good luck, and I'm very interested in what you do and how it turns out.
George