I never understood incubating nightmares for anything, but especially, Lucidbunnie, if you are already hovering on the edge of a cliff in waking life.

Your calling what you seek a "dream version of cutting myself" seems very accurate to me. All you may be doing by forcing nightmares upon yourself is basically torturing yourself, and you are doing so with a medium that can rise up and damage your already challenged psyche deeply, rather than help it.

This is not like smoking a carton of cigarettes to make you sick of smoking (which in my opinion also doesn't work, BTW), nor is it, I believe, some way for you to experience what you imagine your SO to have gone through. In my mind, all a nightmare that accurately duplicates being burned alive does is temporarily hurt and terrify; you will very likely wake up with the exact same feelings you have right now, except for the relief you will have at being still alive (which might lead you to even more terrible feelings, like guilt, and not less).

On top of all that, and as you might already have noted. I also I don't even think you can have a lucid nightmare. Nightmares are not nightmares because of their content or imagery (though that sure helps), they are nightmares because the dreamer believes they are real. If you are lucid, then, you are removing the defining component of a nightmare because you know that nothing you are seeing is real. So when lucid your nightmare imagery falls on the scare meter to something more like a horror movie or roller-coaster ride, which can be exciting, but by no real means nightmarish.

So I think you will find that the folks who successfully incubate nightmares -- for whatever reason they may choose to do so -- tend to incubate the non-lucid kind; the kind where you will feel the pain, and all the fear; where what is happening is very real to you. This in the end, might not be where you want to go...