Out of curiousity (I know nothing about the guy), did he write this in prison?
No, he wrote it while he was living in that tiny cabin in Montana, while he was the Unabomber. His IQ is extreme, but the poor guy was a target of MKULTRA. That's probably why he thought sending parcel bombs to the scientists destroying our species was a good idea.
It's hard to say. It did get his entire manifesto published in a national newspaper, but at the cost of life in prison. This was way before the internet, so it's also likely that he would have had zero impact on society with his anti-technology rants as some random guy living in a cabin. And as I said above, others have picked up on his theories and taken them further.
Not to be too anti-semitic, but the horrific acts against children and people in general by the entities who own and control our planet make no reaction too extreme.