I absolutely agree with your assessment of Jayne. I think buying him the knife was probably the best thing she's done, but a lot of what she's doing is coming from Jayne's own fantasies, and what a person fantasizes and what they find desirable in real life are very different. River's still struggling with that. I do like the idea of Jayne as a skittish horse thought... a big, dangerous, skittish stallion.