Wow. Those little buggers sound dangerous.
As to local anaesthetic effects of capsaicins, the hottest peppers I have ever run into were tiny, dark green, and commonly used in Thailand. I had some Tom Yam soup there with whole peppers hidden in the bottom of it (maybe as a joke on the gringo, I am not really sure). The first sensation upon chewing a couple of these before realizing what I had done was overwhelming fire, but it was followed not long after by my entire mouth and throat going numb. My entire body broke out in a sweat. I have never run into anything remotely like these things since. In Thailand, they are normally cut into tiny rings only a few millimeters in diameter and served in a
small amount of soy sauce on the side. If you want really strong pleasant heat, you use just the liquid soy sauce. If you want incendiary explosions, you include a few rings...
To this day, I am not sure whether including whole peppers in food is normal there, or whether the servers/owners at the tiny restaurant were having fun with the foreigner.