Reality is not a wave function. It's a useful model, but it's absurd to think of it as real and physical.
The cat isn't really both alive and dead. It's either still alive or it died. It certainly knows.
Reality is reality and models are models.
Except that now we are finding the cat is both dead and alive. The question is, which universe do you inhabit? The only way for you to find out is to measure the result, collapse the probability, and determine which reality you inhabit. Your copy (the one you're so desparate to believe doesn't exist, perhaps because s/he threatens your sense of uniqueness, or free will, or whatever), if s/he opens the box and looks, will find s/he inhabits a universe with a different outcome.
As for self determination and uniqueness, this need not really trouble people. In an infinite set of universes, any outcome will be statistical in nature. Like predicting which atom will decay during the half-life of a radioactive material, no prediction can be made as to a particular state (or decision) you or I, as individuals in an indivual timeline, will make. We are still perfectly free to make decisions, and perfectly responisble for their outcomes, regardless of whether the decision we make matches that of 90% of our duplicates, or 0.0001%.
We may not be unique, but that doesn't mean we don't have free will. (Of course, we may not, but that doesn't follow from quantum physics, repetition in an infinite set, or any of the other variations of parallelism that appear more and more to be a fundamental property of our reality).
So people just need to chill, and see where the math and science actually take us. If it turns out we do inhabit a single, unqiue universe, then we get our uniqueness back and those bothered by parallelism are in luck (though it will be a short lived relief, geologically speaking, and ultimately fatal, astrophysically speaking). If it turns out otherwise, then so what? We still live our lives, with or without determinism. Whether we debate that in the context of a single unique timeline, or multiple, perhaps infinite timelines, doesn't really matter.
The only real loser is religion, whic presupposes just the one timeline. But then, religion has a long history of losing out to science and changing its teachings accordingly (like cockroaches, the memes don't die, they just adapt), so even that is unlikely to change if or when the multi-world hypothesis is proven.
So even the most dogmatic mind need not be threatened by either outcome...except perhaps for someone like the character in Star Trek, who is driven mad at the thought of another person in another universe just like them and spends eternity trying to hunt down and kill his duplicate. In which case, if reality is other than what they desire, tough shit.