It's now been another 10 days since my first post and I thought I'd update on my experience thus far as it's always nicer when a thread like this can have a firm line drawn under it.
In those 10 days if anything I've seen a slight worsening of the bout again - so anything the TENS was doing, it was not a long-term solution. It does still provide relief from shadows during the sessions but the nighttime attacks have returned slowly. I also busted again last Friday night and seen little improvement, but it's worth noting because I was not performing this as a TENS-only exercise.
My final conclusion is that, like many things I've tried, the TENS provided some intermittent relief but is not something to get excited about. Due to the safety concerns raised by other members I can't recommend it.