As Adriana says, I suspect your problem is that you are working at the extreme edges of BDSM, at the point where it borders onto almost certainly criminal activity regardless of whether it is consensual or not. I don't think you'll find too much trouble getting hold of stories of this sort of thing but people who actually do it for real? Harder to have them come out and admit it.

I know there are a few amputee fetish sites out there so do a search on them? Branding is a form of mutilation and is about as far as anyone on here will go for real, I suspect. You may also get some people who are into discussing quite extreme interrogation scenes as fantasy. However, I am afraid that is about the limit of what I can tell you about the things you are looking for.