I’ve heard several of these “so and so lbs of pressure” claims in a martial arts setting. I find them questionable.
The first thing that jumps out is the units. Pounds is a force unit, pressure is measured in pounds per square inch (for example), i.e. psi. Pressure is a distributed load, force is a total load.
So when they say 8 lbs of pressure, do they mean 8 lbs, or 8 psi? What force load is required to get 8 psi in the tissue around the testicles?
Another factor is the difference between a slow pull and a quick yank. A quick yank will impart a larger impulse load than a slow pull with the same force, which translates into more damage.
I’m fairly certain you can yank an ear off, though I have not tried it. I am less certain you can actually remove the nutsack, but you can certainly make the guy feel like you did so. (Just checked toodlepip’s links, so it is apparently possible.)
That kind of pain is incapacitating. He won’t be able to do much more than clutch his crotch, maybe limp away. Get out of range, he can’t chase you well.
Striking can be just as effective and easier. Trying to grasp through jeans might be a challenge, for instance. But Chronos is right, men will instinctively protect their crotch if they sense you going for it. A simultaneous or followup to the eyes and/or throat is a good combo.
Just for grins (experimentation), I tried grabbing myself through my jeans. I can’t actually get ahold of anything solid, the jeans are too resistive. However, in the process, I can tweak my nuts enough to hurt. Not incapacitating pain, but enough to flinch. A flinch is a window of distraction. They focus on their nuts, hit them in the eyes. They block their face, knee the groin. They’re blocking both of those, kick them in the knee. Then get away.