If it were me, I wouldn't split it. I would rough it out with a hatchet, which will allow you to follow profile you want. Its thin ringed, but that's not necessarily bad. I think a bigger issue is that the early wood/late wood ratio is pretty inconsistent, so I'm finding it tough to pick a great spot to be the back of the bow. But than again I don't know squat about osage, being a PNW boy.
I'd probably try to make the back of the bow about 22 rings up from the core in the lower picture (assuming the two end pics are oriented the same way). Someone else might disagree and be a lot more smarter than me on this one.
Good luck.
Gabe