I don't remember that specifically, but it would be one of the less crazy things he says. There are sound theoretical motivations for a retro-causal account of quantum mechanics, although a successful retro-causal model of the theory is yet to be constructed (John Cramer's transactional interpretation comes close).
However, I do remember Adams endorsing something like The Secret) in the chapter, where you can change the world to your benefit merely by wanting it enough. I don't entirely recall if he sees this as a consequence of quantum retro-causality, but I think he does, and if that's the case then yeah, the quantum stuff is batshit too.
Yes, he does. It's not necessarily "wanting it enough," though; he specifically instructs that you have to pick a sentence that describes what you want, such as "I want to get rich in the stock market" - specific, but not too specific - and write it, by hand, in a notebook designated for this purpose, at least 10 times each night. He claims that doing this, he did in fact make a lot of money in the stock market, and became the mostt popular cartoonist in the world by a metric he specified (some index, I don't remember which).
Not really ...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.