I'd be relying heavily on my Vet. I've had bigger wounds in my own cats but in places where skin could be drawn together to be stitched over the wound. I'll guess because that's on a skinny cat leg there isn't enough skin to do that with so your Vet is expecting healing by second intention? And that does take a long time.
She lets you poke around in there and clean that out? What a good kitty. What are you taking the white stuff off with?
Sorry, I don't think I've been much help. I think we have some people who work at Vet offices who might come by and be more helpful. It's so good of you to do this, I hope kitty does heal up as soon as she can.