That stave has generous thickness Kirk, so I think if you chase a fat ring (the 3rd you've started) it's no problem. Even the 4th you've started should come off but you arent' completely committed just yet, no farther than you've gone. I need to see the ends of it again to be sure. I'm working from memory. Seems like there were lots of tiny rings, most of which I chased off, then the good fat ones started. I probably chased off 8 or 10 heartwood rings, all tiny, in addition to the sapwood. I know I chased off 3 or 4 one at a time, and tend to take a few when they are little like with the sapwood passes, just gouging out as quickly as my arms will carry me.
I'd imagine the ends look like the leftmost one here. Any of them fat ones is good. All you are concerned with is have one fat continuous ring end to end, with no marks, gouges, nicks or splits in it.
The topmost arrow on the left pic shows you want to get the light colored stuff off the top, but no more. The second arrow underneath is what folks call the crunchy stuff, but that stave is so tight ringed it's crunchy stuff ain't thick enough to actually be crunchy, or even pronounced enough to "feel." But as your pics show, easily found.
The rightmost pic shows sapwood, white wood, which you may not have ever seen on osage in person. But that specimen is far from typical, being an extremely fast growing tree. Most have several smaller whitewood rings, more like the size of the heartwood you see. In this one tree the heart started closer to the bark. You can also see in it (maybe, in person for sure) what are called "lunar" rings, intermixed within the summer growth. Seems like I read its like a mini-seasons within the summer season, where moonlit vs. dark night cycles make their own tiny soft rings within the summer ring. But the tree has to lay down growth really fast to see it usually.
I always get confused about what to call the winter growth, the spongy soft stuff, and the hard, more wood-like summer growth.
Looks like you are off to a good start. I'd encourage you to take one ring at a time. Then if you get a surprise somewhere along the way you got options. Once you started a ring, there's no going back. Also, clean up the knot end, as tedious as it is.