It seems like a good idea to just practice on that wood, but it will almost certainly break before you reach full draw, and exploding bows can have long lasting effects on your shooting! Besides the fact that the wood is already breaking down (and the color does look off, so there's no doubt about that), it would break at those knots anyway. If you have a limb in the middle of a stave in the future, leave more of it on until you can see better; that way you won't violate the ring on the back. I would wait until you can get out to find osage, locust, or a living whitewood. If you can find standing dead osage, that would be ideal of course. Sorry if I sound like a party pooper. Good luck!