Fantastic. I love it. For what it's worth: I'm not put off by Draco being so young - it is Fenrir, after all. He specialises in children. I think it's quite telling that what I find most disturbing (yet very IC, no question) is the fact that Fenrir pushes his long sharp claws into Draco.
I like Fenrir's expression: he seems to have an almost calculated look underneath the leering, observing Draco closely, watching his every reaction and eyjoying to see him suffer.