Hi Kazzar,
I had the whole body twitching/cramping at the onset of my PN. And went through that same ALS paranoia. I completely understand. But it is one of the seemingly less known symptoms of SFN. And unfortunately, the more you obsess about it, the worse it gets. That is a big reason why I always say that stress reduction is one of the key components to dealing with PN. (Here I'm talking like a long timer, but I've only had this for 15 months now

)
Ultimately, I think going through the ALS paranoia was a good thing for me. It made me re-examine every priority in my life. I have had life-long issues with anxiety, but after going through that, I've rarely been bothered by anxiety.
You didn't say if you were taking any medications for your PN. I found that taking gabapentin drastically reduced the twitching/cramping. But it seems like everyone has a different experience with gabapentin, so it may not work the same for you.