I don't think the writer really 'got' most of the jokes. A breakdown of the quotes:
"I was waiting for my girlfriend to come round. Because I'd hit her really hard."
A classic joke structure; subverting the listeners expectations, in this case through wordplay.
Gerry K tells a joke about watching a pimp fighting with two prostitutes. "I'm not having that," he says, "So I joined in - I punched her spark out."
Again, subverts expectations - the listener expects that he will jump in to defend the women, but he actually jumps in to aid the pimp.
"Some audiences say they don't like rape jokes. They say that, but I know what they mean."
Parodying a rapist's mindset.
"Wouldn't it be funny if that girl got raped by, like, five guys right now? Like right now? What if a bunch of guys just raped her ?"
A weak, indefensible attempt to come up with something witty in response to a heckler.
"I fucked her in the arse. I thought I'd really give her something to cry on my shoulder about." Then he said he might "slit her throat from behind, dig a hole in my back garden and bury her".
Again, not really funny or defensible. But notable that Stewart Lee, a very pro-PC performer, also faced criticism after quotes were reported out of context.
"What do nine out of 10 people enjoy? Gang rape."
Subverts expectations, see above.
"Who is going to complain about rape jokes? Rape victims? They barely even report rape."
Clever, in the funny-but/cause-it's-true camp.
Of the seven quotes she uses, only the first one (maybe first three? Article isn't clear) was heard at the Fringe, and that one is a good joke, classic wordplay.