"when you make a sapling bow, how do you split those in half?"
I might split a 4" log, but not a 2", and I wouldn't try that one with all the big knots on one side. What I do on a log like that is run a kerf down each side with the tip of a chainsaw, just an inch or less deep, then drive a wedge into the middle of the log. With knots like that, I'd cut it most of the way through.
The other good method is to saw into the side you don't want, maybe halfway through a 4" log, or whatever, every few inches. More around the rough spots. Leave yourself plenty of wood to make a bow with. Then come along and knock the blocks between the cuts off with a hatchet, machete, or big chisel.