Don't let the title fool you, I'm a fan of Family Guy!!
So how far is too far for Peter...hmm let's see:
He was Death, he is Retarded, he earned the Wrath of God, He had his wife burned and children taken from him, he bought a tank (for Meg) and got it impounded, he busted his wife out of prison, he waged a one-man war against hadicapped people...THE LIST GOES ON AND ON!!!

In short I don't think there's anything else he can do to take the show too far LOL, they screwed around with plenty of topics and have come back from cancellation...they are almost untouchable (i.e. South Park's "Cartoon Wars")

I thought the terminally ill children jokes were a bit close to the knuckle (but still pretty funny)