Why does god want to cut off women's hands?

[Ryantology]

The same could be said of jail time. What's the difference?

The fact that jail is punitive rather than preventative demonstrates that flawed beings sometimes have no choice but to invent flawed solutions to problems. The fact that there's no difference demonstrates that God's law is a flawed solution invented by flawed beings.

It doesn't. As noted, eye for an eye. A man damaging another man's junk would have his own junk damaged - a worse fate than losing a hand IMHO.

Again, damaging the genitals isn't required. Merely seizing them puts a lady down one hand.