Pain based methods are inherently uncertain,as pain tresholds vary invidually and enviromentally. Mechanical disabling,like taking out a joint,cannot be overcome.The short answer to your question is that if you squeeze a man's testicle with even half the force that an average woman's hand can squeeze with, it is going to completely incapacitate him unless he is on some sort of serious anesthetic drug. And even then, I'm not sure. I heard from a guy who got hit with a paint-ball (not even ruptured) who said that the strongest painkillers the hospital had didn't completely stop the pain--if he wasn't knocked out cold, he was still in agony. If you can can crush a half-ripe plum or apricot in your fingers, then you can squeeze hard enough to rupture a testicle, and no man--not even one doped up on PCP--can continue to do anything after that injury.
The force required to rupture a testicle is estimated to be 50 kilos. Most untrained women might find it hard to deadlift 50 kilos with both arms,at least it would likely take several seconds. It takes up to several seconds for a muscular contraction to reach maximum strength output. http://www.emedicine.com/med/byname/...lar-trauma.htm
While some men may exaggerate the durability of the testicles,your writing tends,IMHO,slightly to the direction of a ballbusting fan,who fantasize about being submissive and deny female weaknesses.I've read quite a few postings in various places saying something to the effect that groin attacks aren't as effective as what you see on TV. That's total, ridiculous BS. Why do men say that? Are they scared to admit that they have this weakness?
Very rarely does one see a man shrug off a testicle attack in TV or cinema. Sometimes the effects are even strongly exaggerated,like being incapacitated by a towel whip. Although everyone is an invidual.
If you go to YouTube,you can see a lot of boys volunteering to take fairly hard hits from girls,with varying success. I think that's pretty sad that they do,as it is harmful and sets a questionable example,but the point is a lot of them are willing to do it,while you almost never see a female subjected to the same treatment. Just imagine a woman being peer pressured into taking a haymaker in the face from a grown man. That's not even such a vital area.Yes, there are guys who are into "ballbusting", who enjoy having a woman hit them there. But we're talking light to moderate blows. Even the most hardened masochist can't take a forceful blow there without suffering the usual effects. And as long as he's crumpled to the ground in a helpless, harmless, motionless pile, and you get away unharmed, who gives a crap whether he "enjoyed" it.
That makes me think of breasts. Women are required,recommended or allowed special chest protection in a lot of (combat) sports,so there's one vulnerability men don't have,aside from having more fragile bones,muscles,connective tissues and a higher concentration of nerves around the body leading to more pain. Sometimes the breasts can get even more tender than the testicles,relative to the menstrual cycle,but I'm sure there is invidual variation to that too.As a woman, you have only one severely vulnerable area to defend, and it happens to be right near where you arms attach to your body. You'd be stupid not to take advantage of this basic strategic advantage.
The ovaries are another gender specific weakness,although not necessarily a large one. Under UFC rules,some kicks to the kidneys are banned,which shows that mere internal location of an organ does not render them completely safe.
Finally,it all depends how you define "severely" vulnerable. Women surely have advantages in the nether region department,but also some possible weaknesses,and some of the advantages even out in intergender fights,which is what all of women's self-defense is about. The sensitivity of the vulva is suggested by the fact that it is recognized as a target in self-defense publications.
Second,the pubic bone of the female is likely more fragile,which adds to the severity of an impact. A man can exert quite more power,which would compensate,more or less,for any relative insensitivity to pain and injury.
In addition,at least a few female fighters (such as TKD olympians) have been incapacitated by the strike of a fellow competitor,despite presumably wearing protection. Genital protection is also recommended or downright required in ringette,a sport in which body contact is banned and the plaything is a flexible ring,quite more forgiving than the solid, rock hard puck of ice hockey.
And if he has her undressed,then he can tear her vulva &/or vagina with his hands. A penis can cause injuries there,so it is not surprising.
When a 100 pound woman and a 200 pound man confront,the entire body of the woman will appear like a giant testicle (rather,an ovary) to the man,in terms of vulnerability.