Leave some sapwood on teh skinny split if you need to, just be sure to seal the back really well. Osage sapwood is very wet and notorious for checking badly. A high crown on an ELB isn't that big of a deal though, its not that wide so there won't be that much of a crown.
You might try a backwards bow like you say, I think I'd maybe back it with rawhide though. I've seen very few bows made this way and the majority of them didn't survive very long. Your deflexed stave is trained to be compression wood, it probably won't be as good in tension as a result of growing under the opposite force. Sometimes wood is better as firewood.
Oh and you might start your split on the little log in the middle and work out to each end. Sometimes a split will run off the log on the smaller ones. Starting in the middle with a hatchet head,akm es it where you don't have to go as far to get to either end.
Good luck and keep us posted with pics.